A simmering sex scandal at the top of the European Commission is set to come to a head with new allegations that could derail Angela Merkel’s coalition Government in Germany.

Claims that Günter Verheugen, the second most influential man at the Commission, promoted his lover to chief of staff are to be published in the German media today.

The allegations suggest that Mr Verheugen has lied to the press and perhaps also misled his boss, José Manuel Barroso, the Commission President, who has backed his deputy for the past year.

Speculation surrounding the 63-year-old German Commissioner, who was photographed last year naked on a beach with his adviser, Petra Erler, has been rife. Mr Verheugen has always denied that his relationship with Ms Erler went beyond friendship.

The latest allegations, in the new issue of Bunte magazine, are made by Katrin Fuchs, a German politician, who has been a friend of Mr Verheugen and his wife, Gabriele, for 20 years.

Ms Fuchs says that the commissioner confessed that he was having an affair with Ms Erler in January 2006. “And he then admitted that the relationship with Ms Erler had been going on since the spring of 2005. He was sorry about it, and didn’t know what had got into him,” she says.

In April 2006 Ms Erler was promoted from being a member of his advisory team to become his chief of staff. The promotion of a lover would be a violation of Commission guidelines.

Mrs Verheugen announced last week, also through the columns of Bunte, that she had separated from her husband and was consulting lawyers.

“I can confirm that I have talked at length with Frau Verheugen about these matters,” Ms Fuchs told The Times. Mrs Verheugen was not available for comment.

Angela Merkel, the German Chancellor, has intervened personally with Mr Barroso to back up the beleaguered German representative, according to senior EC sources.

Her fear is that the forced resignation of Mr Verheugen, a Social Democrat, would create a chain reaction in the German Government, which is a coalition of her Christian Democrats and Social Democrats, that could lead its eventual break-up.

The Social Democrats would insist on putting one of their own people in his place – and the only politicians of sufficient seniority are the Finance, Foreign and Environment ministers who are indispensable to the approaching general election campaign. The Christian Democrats, meanwhile, will put Ms Merkel under heavy pressure to place one of their own in Brussels – a clear breach of the coalition agreement between the two parties.

The Commission President has his own agenda: he needs German support for a second five-year term in office. Mr Barroso has taken no action, such as ordering a Commission inquiry, because he claims that Mr Verheugen has cleared up any doubts.

“Nobody has yet been able to come up with any evidence that puts him in a difficult position,” says a Brussels source. “Should there be evidence, then it might be a different matter. Barroso has gone on Mr Verheugen’s word.”

The stonewalling strategy of both Ms Merkel and Mr Barroso has also been undermined by Mrs Verheugen’s announcement that she is to separate.

A divorce case will spill the intimate details of her marriage – and make it plain that Ms Erler, 49, was apparently much more intimately connected to the Commissioner than he has been prepared to admit publicly.

“It’s curtains for Günter,” said a Christian Democrat deputy in Berlin, with barely concealed glee.

Ms Fuchs claims Mrs Verheugen discovered on her husband’s birthday – April 28, two years ago – that he was having an affair. “She wanted to surprise him by driving to Brussels with their dog, Matthes, so that she could be the first to congratulate him at the stroke of midnight,” says Ms Fuchs.

He did not pick up his telephones, even though she rang through the night. When she eventually got through, he admitted that he had been with his lover.

The turning point for the couple, Ms Fuchs, 69, said, came when Ms Erler rang the Commissioner at home in Brühl shortly before Christmas 2005. Mrs Verheugen answered the phone, handed it to the Commissioner who then locked himself in his study.

“After half an hour he returned to his wife and said it was his lover, that he had finished with her and she was trying to change his mind.”

Photographs later showed the Commissioner and his adviser hand in hand on holiday in Lithuania. During the same holiday, in July 2006, he was snapped naked apart from a baseball cap with Ms Erler. This was shrugged off as a cultural oddity: Ms Erler, the highest ranking East German in the Brussels bureaucracy, was said to be a convert to nudist philosophy. The Commissioner took out an injunction to stop further publication of the pictures.

By this time the German press had caught wind of impropriety. Photographs showed Mr Verheugen entering Ms Erler’s house at night and emerging ruffled the next morning. He was also spotted buying roses, apparently for Ms Erler, at a petrol station this summer. When he glimpsed the camera, he crouched low in the back of Ms Erler’s car.

A woman scorned

— Robin Cook, when Tony Blair’s Foreign Secretary, informed his wife, Margaret, that their marriage was over in a VIP lounge at Heathrow Airport, hours before a Sunday newspaper exposed his affair with his personal secretary. Mrs Cook responded by alleging in her book A Slight and Delicate Creature that Cook was a drunkard who altered his views to suit his political needs

— When Birmingham radio DJ Tim Shaw told listeners that he would happily leave his wife and children for glamour model Jodie Marsh, it was too much for wife Hayley – already angered by a previous show in which Mr Shaw said he fantasised about sex with her sister. She put his beloved sports car up for auction on the internet, where it was sold for 50p

— After 14 years with the police, Andrew Clay was described as nearly useless to the force by a superior, after his conviction for the theft of a truncheon on evidence given by his jilted wife. Source: Times archives

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