He was once a rising star, tipped by admirers to become Britain’s first mixed-race prime minister, then suddenly relocated to South Africa as high commissioner. After three years of invisibility, Paul Boateng resurfaced last week in newspaper reports that his wife was accused of bullying their domestic staff.

The Foreign Office’s admission that it is investigating complaints by employees and that a go-between is mediating between them and Janet Boateng comes as a humiliating denouement to the 57-year-old Londoner’s tenure in one of the diplomatic service’s plum postings.

Mrs Boating is said to have accused workers of stealing her underwear and jewellery, and failing to apologise once the missing items were found. According to William Fenyane, a black South African, who resigned as estate manager earlier this year Mrs Boating ordered him to sack local contractors because they were “no good, just lazy South Africans”. Fenyane said he saw Mrs Boateng “square up physically” to her social secretary as if she was going to hit her. Mrs Boateng offended both black and white staff, constantly finding fault and “shouting and screaming” he said.

Next May Boating relinquishes his palatial quarters in Pretoria and his equally magnificent nine-bedroom mansion in Cape Town, where he presided over glittering receptions.

It was a dream come true for Boateng, the first black member of the cabinet, although not quite what he envisaged when, as a left-wing firebrand, he proclaimed on his election as an MP in 1987: “Brent South today, Soweto tomorrow.” Yet he appears to revel in the job’s perks. “Every time I have met him he was hyper-genial,” said one visitor. “He was clearly enjoying himself a great deal.”

On viewing the acres of gardens, swimming pools and tennis courts, Baroness Thatcher once angrily questioned the need for such opulence, saying it exceeded anything available to a British prime minister.

Janet Boateng, a Barbados-born mother of five, oversees the residences, whose local staff include cleaners, cooks, gardeners and security guards. According to the Foreign Office, no disciplinary action has been taken and her husband’s position is unaffected. But some wonder what Boateng has achieved for this luxury. Others say the affair underlines the mistake of handing out diplomatic posts as political rewards.

Earlier this month comparisons were drawn between Boateng and Barack Obama after Trevor Phillips, chairman of the Equality and Human Rights Commission, claimed the US president-elect would have found it impossible to become prime minister in Britain because of “institutional racism” in the party system.

Like Obama, Boateng was the child of a black African father and a white mother and made a meteoric ascent through the political firmament. Like Obama’s wife, Michelle, Janet Boateng retained her core beliefs after her husband completed his “long march to moderation”, as one colleague termed it. It began when Boateng sheared off his black-consciousness Afro and donned dapper pin-striped suits designed by Ozwald Boateng, who is no relation.

Janet Boateng earned a formidable reputation as a social worker and Lambeth councillor, where her campaign to stop white parents adopting black children brought her into conflict with her husband’s views. Earlier this year, Boateng rejected the “British Obama” label, except to say “that Mr Obama and I both have roots in this part of the world and no doubt he would count himself fortunate, as I do, to have been given so many opportunities in life”.

Critics say Boateng is no Obama. “Obama’s prime qualities are discipline and an icy cool demeanour,” said a senior political journalist. “One of the reasons that Boateng’s political career stalled was not the colour of his skin, which might actually have helped him a bit, but because he had the wrong temperament – he shot from the hip and was gaffe-prone. The politicians who last longest in cabinet are those who are calm, don’t make mistakes or fall out with people.”

Still, nobody doubted Boating’s “lifetime passion” for South Africa and development, even if the First Division Association, which represents senior civil servants, suspected “cronyism”. Yet, as the months went by after his installation in Pretoria, people began to question why Boateng’s passion did not translate into remonstration against South Africa’s failure to restrain President Robert Mugabe’s excesses in Zimbabwe. American envoys, by contrast, had shouted from the rooftops.

RW Johnson, The Sunday Times’s South Africa correspondent, recalled Boateng’s arrival in 2005: “President Thabo Mbeki was then at the height of his power and everyone was kowtowing to him. Boateng evidently decided this was the game to play and was prominent in singing Mbeki’s praises.”

Boateng’s speeches purloined Mbeki’s favourite phrases, such as “the African renaissance” and “the African century”, to the extent that opposition MPs grumbled that the high commissioner “acts as if he’s a praise-singing ANC MP”.

He also caused astonishment by swathing the high commission with a giant ribbon to mark an ANC government campaign, 16 Days of Activism for No Violence against Women and Children. This jumbo-sized salute back-fired two months later when Boateng’s 21-year-old son Ben was accused of raping a girl aged 17. Ben, who denied the allegation and said the sex was consensual, was cleared.

Boateng upset democracy campaigners in September by attending the lavish birthday celebrations of King Mswati III in neighbouring Swaziland, at which Mugabe was a guest. Protesters said the £7m spent on the event would have been better used tackling the country’s unemployment, nutrition and HIV epidemic. Asked why he had not reproached Mbeki for dismissing the Aids epidemic and indulging Mugabe, Boateng told a press conference that he was not prepared to criticise the president for anything.

Paul Yaw Boateng was born in Hackney, east London, on June 14, 1951, and was soon enjoying a life of luxury in Ghana where his father, Kwaku Boateng, was a barrister and a cabinet minister under Kwame Nkrumah. When the latter was ousted by a military coup in 1966, Kwaku was thrown into prison. Boateng’s mother, Eleanor, a Scottish Quaker, fled to Britain with the 14-year-old boy and his sister.

The family moved to Hemel Hempstead, Hertfordshire, where Boateng excelled as a pupil at Apsley grammar school. Graduating from Bristol University, he became a civil rights lawyer. He emerged in the 1970s as a radical Bennite, the scourge of miscarriages of justice and the “sus law” hated by the black community.

Elected to the Greater London council in 1981 as a supporter of Ken Livingstone, he became chairman of the council’s police committee and was an outspoken critic of police relations with ethnic minorities. But his official role soon incurred a backlash from black activists.

Roy Kerridge, a writer for The Spectator, recalls being saved from a mob by Boateng in 1983. Boateng, chairing a “virulent” conference in protest against the Criminal Evidence Bill, arrived late to find that Kerridge had been violently ejected. Decreeing that the journalist could return in the interests of democracy, Boateng faced down the mob. “I said he could stay!” Boateng roared, only to be accused of being “racist” himself.

Kerridge viewed the young radical with new respect: “His career appeared to be in ruins, as taunt after taunt was thrown at him from the mob.” Eventually they both escaped.

Boateng grew more moderate under the leadership of Neil Kinnock, who brought him to the front bench as Treasury spokesman. Tony Blair appointed him a junior health minister in 1997. A year later, he became a Home Office minister, then minister for young people. He joined the Treasury as financial secretary in 2001. He was promoted to chief secretary the following year.

Although affable, he was never popular in the party, where he was regarded as pompous and a poor performer on Radio 4’s Today programme. At the 2002 Labour conference, he was given a slow handclap for a long-winded speech in defence of the private finance initiative. His career seemed to wilt in the shadow of Gordon Brown, the chancellor. “Paul hated the Treasury and has wanted out for ages,” a senior ministerial colleague claimed.

“He wasn’t seen as a safe pair of hands,” said a political journalist. “If he was on the radio, journalists would tune in because you could never be sure what he would say next.” Just as his sacking was predicted, in March 2005 he announced he would not stand for reelection as an MP and was taking up the post in Pretoria.

In an interview with The Spectator earlier this year, Boateng hinted that he may have unfinished business at Westminster. Politicians must surmount “a disconnect” with the people they represent, he said. But first he has to surmount a little local difficulty.

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