An MP has warned he could resign from the Government if Britain goes to war against Iraq without United Nations backing.

Hastings and Rye MP Michael Foster is one of a band of ministers and parliamentary aides who have threatened to quit as tensions mount for Tony Blair.

Mr Foster, who is parliamentary private secretary (PPS) to Attorney General Lord Goldsmith, said his stance was about upholding the authority of the UN.

He said: "There is a point where you have to decide whether this is right or wrong."

Mr Blair is facing a growing crisis with the deadline for Saddam Hussein to disarm set for March 17. He is working to win over doubters on the United Nations Security Council.

But Russia, France and China show no signs of supporting the crucial second resolution.

Mr Blair has made it clear he will take military action without a fresh resolution if he considers any veto by these countries "unreasonable".

In a blow to Mr Blair, International Development Secretary Clare Short said she was also considering resignation.

Ms Short said she could not "stay and defend the indefensible".

"The whole atmosphere of the current situation is deeply reckless - reckless for the world, reckless for the undermining of the UN in this disorderly world, reckless with our government, reckless with his own future, position and place in history."

Loughborough MP Andy Reed has announced he has quit as parliamentary aide to Environment Secretary Margaret Beckett.

A PPS is an unpaid position, seen as the first rung on the ministerial ladder.