John Major and Lord Lamont have reportedly asked for Treasury documents covering the events leading up to Black Wednesday in 1992 to be kept secret.

The papers, which should have been published under the Freedom of Information Act last Tuesday, have not entered the public domain because Sir Andrew Turnbull, the Cabinet secretary, is allowing the prime minister and chancellor at the time of the events more time to study them, report the Times and FT.

Britain left the European exchange-rate mechanism on Wednesday September 16, 1992, after the Bank of England reportedly spent £27 billion of reserves in a futile attempt to support sterling.

Major's office denied any attempt of a cover up and said he was on a lecture tour in America this week.

"There is no attempt to play for time," an official said. "He will look through this next week."

Lord Lamont commented: "I am relaxed. I will read the papers. They are being delivered."

The Tories said the Treasury was trying to rush out the documents in an attempt to score party political points.

Co-chairman Liam Fox commented: "The government should not be allowed to manipulate the law, releasing information it believes damaging to its opponents while refusing to answer questions about its own conduct."