More than 50 former British diplomats have called on Tony Blair to get tough with President Bush over the approach to Iraq and the Middle East.

The attack on the prime minister came from several former Foreign Office officials who served in the region.

They urged the government to stand up to US policies that are "doomed to failure".

"The conduct of the war in Iraq has made it clear that there was no effective plan for the post-Saddam settlement," an open letter said.

"All those with experience of the area predicted that the occupation of Iraq by the coalition forces would meet serious and stubborn resistance, as has proved to be the case.

"To describe the resistance as led by terrorists, fanatics and foreigners is neither convincing nor helpful."

Number 10 said it would respond to the letter "in due course".

"They are entitled to their views. What I would stress is that our objectives both in Iraq and the Palestinian conflict remain stability, peace and freedom in the Middle East," a Downing Street spokesman said.