Iain Duncan Smith has faced Tony Blair at the despatch box for the last time.

The opposition leader, who was last week ousted by his own MPs, used the opportunity to praise the "extraordinary" work of British forces in the Gulf.

Seeking initially to downplay the occasion, he called on the prime minister to say who was arming and funding those who are mounting a concerted effort against allied troops.

He said many people had "growing concerns" about the actions of those pitted against service personnel and aid workers.

Noting the event, the prime minister paid tribute to his opposite number.

"Whatever our differences, and there have been a few, I wish him well in the future," he said.

But later in the half hour session Duncan Smith took a measured sideswipe at his opponent.

The Tory leader said: "I've asked the prime minister this question 18 times, fat lot of good it's done me frankly over the last two years, but I'm going to give it one more try.

"Why does the prime minister persist in denying the people a chance to vote for a referendum on the EU constitution?"

Blair said the proposed constitution "does not involve a fundamental change" and reminded Duncan Smith that he had been out of step with his party over the Maastricht Treaty.

Duncan Smith, however, warned his opposite number that some on his own benches were at odds over the issue.

Labour had presided over 37 different referendums, he said, repeating his demand for an EU poll.

"Is the prime minister really telling all of us that an elected an elected assembly for Hull, an elected monkey for Hartlepool, are more important than an elected president for Europe?" he asked.

And bowing out for the last time he warned Blair that ignoring the dissent was high risk.

"I must say to the prime minister, just between the two of us, I have a sixth sense these about a leadership challenge bid I must tell him, so he should watch very carefully," he said.

"The prime minister still persists in saying that the constitution doesn't change anything and is just a tidying up exercise.

"So Mr Speaker, by common accord, for the last time, that's the reason why nobody believes a word he ever says anymore."

On Thursday, Duncan Smith is expected to hand over control of the party to Michael Howard - who is the sole candidate seeking the leadership.

Whilst his performance on the frontbench has improved since the croaky days of October 2001, he has rarely trumped the Labour leader.

Recent attacks on the honesty of the prime minister have roused some of the Tory troops but led others to question the judgement of their outgoing leader.

For many the sometimes disproportionate response was evidence that Duncan Smith lacked the acute political judgement required for the top job.

And whilst he initially avoided the question of Europe, he has turned up the volume on the issue over recent months - choosing the issue for his valedictory Commons appearance.

Last week Labour MPs heckled the Tory leader, who was just hours away from a no confidence vote, with uncharitable chants of "bye bye".

But this time the House showed Duncan Smith good grace as he exited following what he has described as a "near death experience" at the hands of his opponents.

Similarly the prime minister, who is now bracing himself for the intellectual and rhetorical skill of Howard, sought to avoid a bloody confrontation.

Whilst Duncan Smith rose to Labour cheers, the early exchanges across the floor of the House were heard in near virtual silence.

All that remains now is for Duncan Smith to move quietly to the Tory backbenches.