Pressure is mounting on the foreign secretary to explain his decision to continue arms sales to Israel.

The calls followed backbench criticism of government moves to authorise the export of components to be used in F16 fighters destined for the Israeli air force.

Foreign secretary Jack Straw announced in a written answer on Monday that any UK move to block the export of components for use in the United States-built aircraft would have "serious implications" for defence relations with the America.

But MPs lined up on Tuesday to condemn Straw's failure to come to the House and explain his new policy.

The Labour MP for Cynon Valley, Ann Clwyd, said reports indicated that Israeli defence forces were using the planes against West Bank targets.

"I think it is totally objectionable that we should be selling even a component for any more munitions to Israel that could be used against the Palestinians," she said.

And fellow backbencher Alice Mahon said the foreign secretary had "effectively changed government policy".

"Selling parts of F16s to the Israeli government will simply cause more destruction in densely populated refugee camps because as we've seen the Israeli defence force will use them against civilians," said Mahon.

Father of the House Tam Dalyell said there should be an explanation from the foreign secretary on what relations with the Americans were under threat.

"I think the House of Commons deserves some explanation as to precisely what these relations with the Americans amount to, and are we to do the bidding of the Americans, whatever they ask, even if it means jeopardising the British position in the Middle East?"

In Monday's written answer Straw said that UK is to supply Head Up Display units for the US for planes which are scheduled for delivery to Israel in 2003.

Earlier this year the government effectively banned military exports to Israel following the use of British-made vehicles in the occupied territories, but the latest announcement means a partial abandonment of that policy - Israel has used its war planes in attacks on what it describes as Palestinian terrorist targets.