Nick ‘no more than 30 lovers’ Clegg, a wild party in Paris and why his wife lost her sense of humour

But when a newspaper article described the bed-hopping antics at a party he attended – including details of the amorous adventures of a certain "Nick" – Miriam took a less sanguine approach.

The piece, written for the normally staid Financial Times by Rachel Johnson, sister of Tory MP Boris Johnson, described a Millennium Eve party Ms Johnson had spent with Mr Clegg. She included a reference to "Nick" spending the night with a woman he had just met.

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Confusion: Liberal Democrat leader Nick Clegg with wife Miriam

At the time, Mr Clegg – dubbed 'Cleggover' after his revelations – had been dating Miriam for eight years and was an MEP.

Soon, to Miriam's fury, rumours had spread through Brussels that the story referred to Mr Clegg, who had featured in a previous article by Ms Johnson. Eventually an embarrassed Ms Johnson was forced to assure Miriam that she meant a different Nick.

In her article, Ms Johnson recounted how she attended a party at the British Embassy in Paris, thrown by political counsellor Simon Fraser.

After the group had watched fireworks at midnight, she said a group of men headed off into the night.

She wrote: "In the morning, wandering past other bedrooms, it was clear that we were the only ones who had slept in Simon's house."

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One of the men later told her what had happened. She wrote: "Nick – who still wasn't back – had gone off with a girl."

Last night, Ms Johnson said she had been forced to put the record straight after rumours spread. "Oh no. Not this.

"It is unfortunate that she [Miriam] thought I was referring to him," Ms Johnson said when asked about the confusion.

Rachel Johnson wrote about the antics in Paris

"I tried to apologise immediately. The thing is there were two Nicks at the party – one was a wild singleton, while Nick Clegg was, of course, clearly wildly in love with Miriam."

Mr Clegg married Miriam in 2000, a few months after Ms Johnson's piece appeared.

One resident of Brussels at the time said: "I think it's fair to say that Miriam lost her sense of humour for a while, and it was all a bit awkward until Rachel put it right."

It wasn't the first time Ms Johnson had written about Mr Clegg's social life.

Two years earlier, when Mr Clegg was still single and was working for Sir Leon Brittan's trade commission, Ms Johnson had included him in an article which described Brussels as a city "full of married men who think they are single."

A spokesman for Mr Clegg said: "We are not going to comment on a story that is not about Nick. We would take very seriously any article which repeated that initial confusion."