Ministers are coming under pressure to reveal the contents of a secret nuclear weapons treaty which has been renegotiated with the US.

MPs demanded a full debate on the updated mutual defence agreement based on a treaty first negotiated in 1958 and regarded as a cornerstone of the special relationship.

The White House this week announced the amended treaty had been sent to the US Congress to be ratified.

"In light of our previous close cooperation... I have concluded that it is in our interest to continue to assist them in maintaining a credible nuclear force," President George Bush said.