More than a dozen female friends, mosty with a media background, have been invited to stay the night.

Guests include Rupert Murdoch's wife Wendi and his daughter Elisabeth, the television presenter Claudia Winkleman and newspaper editor Rebekah Wade.

It is thought Mr Brown will be at Chequers, the prime minister's country residence, at the time but will not be involved in the party which is being paid for by the Browns.

Since moving into Downing Street a year ago Mrs Brown has kept a much lower public profile than her predecessor Cherie Blair and has avoided celebrity parties.

But her professional background is in public relations and she has many successful friends in the media world.

A Downing Street spokesman said: "She is having a group of friends over for dinner and they are staying over. There are just over a dozen of them coming.

"I should stress there will be no cost to the taxpayer because it is a private party and the Browns themselves will be paying for the food, entertaining and costs relating to the use of the Chequers bedrooms."

Chequers, which is south-east of Aylesbury in Buckinghamshire, has been the official country retreat of British prime ministers since the 1920s.