Iran warned today that it could impose new limits on its cooperation with the UN's nuclear watchdog after an unusually critical report from the agency.

The warning came from Ali Larijani, the country's former nuclear negotiator, in a tub-thumping declaration only moments after his election as parliamentary speaker. Mr Larijani is a conservative heavyweight who has been critical of President Ahmadinejad and stood against him in the 2005 election.

The International Atomic Energy Agency (IAEA) yesterday expressed its "serious concern" that Iran was withholding information needed to establish whether it tried to make nuclear weapons, as well as defying UN demands to suspend uranium enrichment.

The report marked a tougher line from the IAEA, which has conducted four years of investigations into Tehran's nuclear programme but has never drawn a conclusion over its nature.

But in his speech to parliament - which drew chants from the chamber of "God is great" and "Death to America" - Mr Larijani warned the IAEA that if its reports were not more “balanced” in the future it would harm cooperation between them. “If they want a more sincere co-operation with Iran they need to have more balanced reports and not look to create a media frenzy," he said.

Mr Larijani also accused the IAEA of "clandestinely" passing its reports to the "5-plus-1" group - the five permanent members of the UN Security Council and German who together handle the Iranian nuclear issue - and added: "This parliament will not allow such deception."

The Security Council has imposed three sets of sanctions against Iran for its refusal to halt enriching uranium - a process that can be used to generate electricity or nuclear arms. “Should this behaviour continue, the parliament...will set new limits on cooperation with the IAEA,” said Mr Larijani, who quit as nuclear negotiator last year over difference with Mr Ahmadinejad.

The tone of the IAEA report, which suggested that Tehran continues to stonewall the UN watchdog, revealed a glimpse of the frustration felt by IAEA investigators trying to unravel Iran's past nuclear activities.

In the past, Iran had extensive voluntary cooperation with the IAEA beyond its obligations under the Nuclear Non-Proliferation Treaty, including allowing IAEA inspectors to visit its military sites as a goodwill gesture to build trust.

But Tehran ended all voluntary cooperation with the IAEA, including allowing snap inspections of its nuclear facilities, in February 2006 after being reported to the U.N. Security Council. Ever since, Iran has limited its cooperation to only its obligations under the NPT. The treaty does not require Iran to allow short notice intrusive inspections of its facilities.

Mr Larijani did not specify what limits parliament might impose on its cooperation with the IAEA.

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