Iran today set itself on a collision course with the West by announcing that it was escalating its contentious nuclear programme.

Mahmoud Ahmadinejad, the republic's new hardline President, has reportedly given orders for a fresh batch of uranium to be brought to the plant in Isfahan for processing from next week.

Reports suggest that Iran has produced 6.8 tonnes of enriched uranium - theoretically enough for a single bomb - since resuming activity at the plant in August, in defiance of an agreement with Europe.

The latest move to heighten tensions with the West comes hours after The Times revealed that the President had ordered a purge of senior ambassadors. The envoys, who were appointed by Mr Ahmadinjed's two most recent - and more moderate - predecessors, are considered too liberal by the new administration.

At first it appeared that about 20 had been recalled to Tehran. It emerged today that as many as 40 heads of mission and other top diplomats have been sacked or reassigned, in the biggest shake-up since the Iranian Revolution of 1979. The majority were appointed during the decade of rapprochement that Mr Ahmadinejad has abruptly reversed.

President Ahmadinejad today cemented 24 hours of international brinkmanship by installing a former comrade in the Iranian Revolutionary Guards to the important position of Oil Minister.

His increasingly aggressive foreign policy has fuelled anti-Western sentiment in Iran, leading to another huge demonstration in Tehran today. It has also caused questions over the possibility of future military action.

Tony Blair, who reacted furiously to President Ahmadinejad's call last week to "wipe Israel off the map", said today: "Nobody is talking about the invasion of Iran."

But, speaking in his capacity as President of the European Union, he added: "The Iranian government has got to understand that the international community simply will not put up with their continued breach of the proper and normal standards of behaviour."

The International Atomic Energy Authority is due to release a report on Iran's nuclear programme later this month. Iran denies wanting nuclear weapons, insisting its atomic ambitions are limited to the peaceful generation of electricity - but many fear that it is cover for the production of weapons.

Four of the sacked envoys, the ambassadors to London, Paris and Berlin and the representative to the United Nations in Geneva, were involved in months of delicate mediation between Iran and Europe over Tehran’s nuclear programme.

One of the most prominent victims of the diplomatic cull is Mohammad Hossein Adeli, the urbane, American-educated Ambassador to London, who has served only for 12 months and is the first Iranian envoy since the Islamic Revolution who speaks fluent English.

Mr Adeli, 52, will be leaving the foreign service in the coming weeks, along with the Iranian envoys to Paris, Berlin, Geneva and Kuala Lumpur. Iran’s ambassadors to Indonesia, Kazakhstan and several Arab states are also believed to be on the hitlist.

"Obviously the new Government wants to have its own people and many of these ambassadors were supporters of (the former President) Rafsanjani and were pro-reform," a Western diplomat in Tehran told The Times.

The nuclear issue is likely to dominate a meeting of the International Atomic Energy Agency (IAEA) board of governors scheduled for this month, and Iran could face sanctions if its case is referred to the UN Security Council.

But the hardening of Iranian policy is not going unchallenged at home. Mr Ahmadinejad may have won a landslide victory but he still has powerful opponents.

The appointment of the unknown Sadeq Masouli to the position of Oil Minister is likely to further stoke the domestic disputes.

"Ahmadinejad is clearly out of his depth," said Ali Ansari, an Iranian expert at Exeter University. "It will have to be resolved internally. There is a view in Iran that if you give him enough rope, he’ll hang himself. But how much rope will it take?"

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