The prime minister has admitted that the US-led coalition "may never find" any Iraqi weapons of mass destruction.

Tony Blair told senior MPs on Tuesday that he had to accept that no stockpiles had been found.

When pressed on the issue on previous occasions, he has preferred to adopt a "wait and see" approach.

But while the Iraq Survey Group has not yet issued its final report, it has failed to locate any significant quantities of biological or chemical weapons.

Blair said he now had to "accept we haven't found them and we may never find them".

But he cautioned that Saddam Hussein could have had the weapons "removed, hidden or destroyed".

The prime minister insisted that the failure did not mean the war was illegitimate.

He insisted that the former Iraqi regime still posed a security threat and had been in breach of United Nations security council resolutions.

At the weekend, former UN ambassador Sir Jeremy Greenstock also admitted intelligence on Iraq's weapons of mass destructions had been "wrong", although he said the government had been right about Saddam's intentions.

The issue has moved back up the political agenda ahead of the publication of Lord Butler's report on UK intelligence on Iraqi weapons.