The station said last month it was in discussion with representatives of Ms Lewinsky concerning a possible interview in which she would discuss her relationship with Mr Clinton.

The £400,000 deal was finally signed for the original asking price after "editorial" negotiations.

The interview will be conducted by Channel 4 news anchor Jon Snow who will be "both tough and fair" with Miss Lewinsky.

The deal means Channel 4 can cash in on the worldwide rights for the exclusive - the planned American network television interview is restricted to screenings in the United States and Canada.

Monica Lewinsky with confidante Linda Tripp

Head of News, Current Affairs and Business David Lloyd said: "This is a real coup for Channel 4."

Other UK stations had also been interested in interviewing Lewinsky.

Media magnate Rupert Murdoch, who owns Fox TV, is reported to have offered her $3m for a "kiss and tell" account that would include a television interview and book.

Channel 4 insists, however, that the lengthy negotiations were not over money.

A source said: "The problems have been about what she can and cannot say.

"We have been talking to her lawyers and are now happy we are going to have an interview with some editorial value.

"If you think of the questions you would like to ask Monica Lewinsky, I am sure those will be the questions Jon Snow will ask."

Roseanne Barr : Rumoured to have offered $1m for interview

The interview will be conducted in the United States on a date yet to be fixed and will be transmitted - probably in February - within hours of her American interview, which is believed to be with Barbara Walters.

It will precede publication of Andrew Morton's planned book with Lewinsky.

Already Channel 4 has had expressions of interest from heavyweight broadcasters around the world to buy rights to the interview which, because of the heavy outlay, it expects to cover its costs.