It would not be right to threaten Iraq with nuclear action now - but if its weapons programmes were not tackled it might eventually become the only option, the Conservative leader has warned.

Tory leader Iain Duncan Smith said the nuclear option was not proportionate to the threat currently posed by Saddam Hussein.

I do not believe any momentum has been lost

Jack Straw Foreign Secretary

It has also emerged that Tony Blair has agreed to face detailed questioning about Iraq from a joint session of the Parliament's defence, foreign affairs and intelligence select committees.

Donald Anderson, chairman of the Commons defence select committee, told the ePolitix.com website the prime minister had agreed "in principle" to the idea.

Foreign Secretary Jack Straw on Tuesday rejected suggestions that momentum in United Nations talks on Iraq had been lost because of Iraq's offer to readmit weapons inspectors.

Need for new resolution

Mr Straw said: "The international community has to take account of the fact that only by resolute action and resolutions of the Security Council that we are going to deal with the central threat posed by Iraq."

Talks about a fresh resolution continue at the United Nations and Mr Straw would not discuss the details.

A new UN resolution was needed so Iraq again got the message if it did not comply with the resolutions, military action would have to follow, he said.

Duncan Smith says he has been pushing for more debate

Baghdad's offer to give weapons inspectors unconditional access appears to have split the Security Council.

Russia says the offer means no fresh resolution is needed.

But UK ministers are treating the offer with scepticism and Tony Blair has insisted the international pressure on Iraq must continue.

Mr Duncan Smith said the offer showed Saddam Hussein was "panicking".

The threat of military action must remain until his weapons programmes were eradicated and constantly checked, he argued.

Former Prime Minister John Major has delivered an implied rebuke to Mr Duncan Smith for not raising questions about the aftermath of a possible war.

Mr Duncan Smith said he had been underlining the need to tackle Iraq's weapons programmes since 1995 and calling for debate about what happened post-Saddam.

'Out of proportion'

He was asked on BBC Radio 4's Today programme whether it would be right to threaten to "nuke" Baghdad if Saddam Hussein used chemical or biological weapons against UK and US troops.

Mr Duncan Smith replied: "I don't think that is a proper way in which to deal with the threat, simply because I think it is out of proportion with the threat that at the moment he poses.

"That's the point that makes the importance of what we're talking about in terms of military action.

John Major implied nuclear retaliation was threatened in 1991

"If we don't and aren't prepared to eradicate these programmes that he possesses now then you will be left with only that option in a few years time."

Mr Duncan Smith has already warned that Iraq may be working on ballistic missiles that could reach Europe.

On Wednesday, Mr Major, Prime Minister during the Gulf War, implied nuclear action had been threatened in 1991.

Iraq had been given an "unmistakeable message" about the response it could expect if it used chemical and biological weapons.

Protect

Now policy makers would be considering whether Saddam Hussein would seek to cause "maximum chaos" and possibly even target a foreign capital.

"We can prepare against that, we can largely protect against that - don't press me how," added Mr Major.

MPs return to Westminster on Tuesday when Parliament is recalled from early from its summer break.

On the same day, the government's dossier of evidence against Iraq will be published.

Mr Duncan Smith said it was not enough for Tony Blair to make a statement and answer some questions.

He should lead the Iraq debate himself, rather than leaving it to Foreign Secretary Jack Straw.