A MILLIONAIRE aristocrat and one-time Downing Street adviser is under investigation by detectives probing an alleged international immigration racket.

Christopher Monckton, a former adviser to Lady Thatcher when she was prime minister, is at the centre of a criminal inquiry into claims that hundreds of eastern European migrants were brought to Britain on bogus visas.

Investigators at the National Crime Squad have raided a London-based employment firm that uses Monckton as an immigration adviser.

Monckton is credited as the brains behind the Thatcherite policy of giving council tenants the right to buy their homes. A scion of a famous Tory family, his sister is Rosa Monckton, who was a friend of Diana, Princess of Wales, and is chairwoman of the committee that selected her memorial fountain in Hyde Park.

He is said to be infuriated by the police inquiry, which he says is entirely spurious. His lawyers have filed papers against David Blunkett, the home secretary, claiming he is being persecuted in a “deliberate, secret and unlawful discrimination” by the government. The case is due to be heard in court during a judicial review set for December.

Detectives say they are looking into allegations of “large-scale illegal immigration”. According to police files seen by The Sunday Times, the case involves “forged Home Office documents, passports, visa applications, stamps, paper and associated items”.

The inquiry began after nine eastern European migrants were arrested in Kent in March. The Home Office moved to block hundreds of visa applications, in which Monckton was involved, from eastern European migrants. They included more than 400 Polish workers who had obtained visas to work in Britain as “self-employed” business people in hotels, restaurants and factories.

Home Office caseworkers were instructed that “Christopher Monckton applications should not be dealt with under any circumstances”. In a letter to Monckton’s lawyers in May, Paula Higson, the director of the Home Office’s managed migration division, said the applications had been rejected by Blunkett “because, on the available information, it appeared likely that those applicants would have been engaged as employees and not as self-employed individuals ”.

In a court document, detectives said they needed to search the London company because the alleged offences involved “serious harm to the security of the state”.

The document, signed by a district judge, said officers were “carrying out a criminal investigation into the (company’s) legal adviser Christopher Monckton”. Monckton’s friends suspect there may be an ulterior motive because of rows over immigration that he has had with the Home Office.

A former journalist and businessman, Monckton, 52, rose to prominence in the early 1980s as special adviser to Thatcher’s Downing Street policy unit. After leaving full-time government he became a political consultant.

He advised the late Sir James Goldsmith when he was setting up the Referendum party and last year he helped the People’s Alliance, a Tory breakaway group that planned to field candidates in the Scottish parliament elections.

The former Tory grandee is from a well-connected land-owning family. His father, Viscount Monckton of Brenchley, is a retired major general who owns a 400-acre farm in Harrietsham, near Maidstone, Kent, and his grandfather Walter advised George VI during the 1936 abdication crisis.

He has three brothers, one of whom is a former Benedictine monk, and has a reputation for eccentricity. He once said that everyone with Aids should be quarantined. He lists romance, clocks and sundials, number theory and punting among his recreations in Debrett’s Peerage.

In 1999 he invented the Eternity puzzle, a complex jigsaw that was supposed to be almost impossible to solve. Monckton put up a £1m prize, which he had to pay out after just a year to an unemployed Cambridge mathematician.

Said by friends to have a £10m fortune, he gave it all to his wife Juliet during a ceremony several years ago. He boasts that all he has to his name is a 1950s motorcycle and the clothes — usually a kilt — that he stands in.

The couple lived until three years ago in a 67-room mansion in Aberdeenshire with 200 acres and the title Laird of Crimonmogate. They sold it for £1.5m and moved to a home on the shores of Loch Rannoch with 90 acres and a mile of shoreline.

This weekend Monckton said he could not discuss the police investigation because of the judicial review. However, a friend said he had done nothing wrong and had no knowledge of forged documents.

The friend said: “Christopher hardly fits the profile of a mafia consigliere . . . He thinks there may be a vendetta against him because he has a track record of embarrassing the Home Office when it has previously tried to take action against this company. This is a spurious investigation and he is confident it is going nowhere.”

The Home Office refuses to discuss the case. However, a spokesman said: “We are resisting Mr Monckton’s application for judicial review very strongly.”

Explore UK News

• Crime News

• Education News

• Health News

• Scotland News

Times Recommends

• Margot Fonteyn: In her footsteps
• Forget beautiful people, let's have wonky Brits
• Fundamentalist brew: faith and power