US troops are secretly using outlawed napalm gas to wipe out remaining insurgents in and around Fallujah.

News that President George W. Bush has sanctioned the use of napalm, a deadly cocktail of polystyrene and jet fuel banned by the United Nations in 1980, will stun governments around the world.

And last night Tony Blair was dragged into the row as furious Labour MPs demanded he face the Commons over it. Reports claim that innocent civilians have died in napalm attacks, which turn victims into human fireballs as the gel bonds flames to flesh.

Outraged critics have also demanded that Mr Blair threatens to withdraw British troops from Iraq unless the US abandons one of the world's most reviled weapons. Halifax Labour MP Alice Mahon said: "I am calling on Mr Blair to make an emergency statement to the Commons to explain why this is happening. It begs the question: 'Did we know about this hideous weapon's use in Iraq?'"

Since the American assault on Fallujah there have been reports of "melted" corpses, which appeared to have napalm injuries.

Last August the US was forced to admit using the gas in Iraq.

A 1980 UN convention banned the use of napalm against civilians - after pictures of a naked girl victim fleeing in Vietnam shocked the world.

America, which didn't ratify the treaty, is the only country in the world still using the weapon.