The Prime Minister will speak at the annual General Assembly of the Church of Scotland where Mrs Thatcher, now Lady Thatcher, set out her credo.

The event at a building on The Mound in Edinburgh is the May gathering of the Church of Scotland's ruling body. Mr Brown's father was a Church of Scotland minister.

Mrs Thatcher's "Sermon on the Mound" to the general assembly on May 21, 1988 dwelt much on personal responsibility, and was attacked by her critics.

"We are all responsible for our own actions," she told the gathering. We can't blame society if we disobey the law. We simply can't delegate the exercise of mercy and generosity to others."

Mr Brown's spokesman said that nothing should be read into the fact that the Prime Minister's speech comes almost exactly 20 years after Lady Thatcher's famous address.

At a regular daily briefing of reporters in Westminster, the spokesman declined to reveal details of the contents of the speech, but said it would not focus particularly on Scottish issues.

Asked if Mr Brown, like Lady Thatcher, would use the occasion to discuss his own moral beliefs, the spokesman said: "When speaking to a Church of Scotland audience, it would be surprising if he didn't talk about his own upbringing, but it has not been the Prime Minister's habit to talk about his own individual religious views."