Iran's new parliamentary Speaker has used his inaugural address to give warning that Tehran could set limits on future co-operation with the UN's nuclear watchdog, after an unusually critical report from the agency. Ali Larijani's stern message, delivered only moments after he was voted overwhelmingly into the powerful new post yesterday, signalled his intention to adopt a tough stance on the nuclear issue.

Diplomats were hoping for a less confrontational tone from the former nuclear negotiator for Iran, who is seen as the main challenger to Mahmoud Ahmadinejad, the hardline President of the country. Mr Larijani fell out with him last year about how to handle the nuclear row with the West.

The International Atomic Energy Agency (IAEA) issued a report on Monday saying that Iran's alleged research into nuclear warheads remained a matter of serious concern and Tehran should provide more information on it. The report marked a more robust line from the IAEA, which has conducted four years of investigations into the nuclear programme of Tehran but has never drawn a conclusion over its nature. Western powers called for more pressure on Iran, which has been hit by three rounds of UN sanctions for refusing to suspend uranium enrichment programmes.

When he addressed parliament, Mr Larijani accused the IAEA of sharing information about Iran's nuclear file with critics of Tehran in the UN Security Council. “If they continue along this path, the new parliament will intervene in the case and set a new line for co-operation with the IAEA. 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,” said Mr Larijani, whose remarks drew chants of “God is great” and “Death to America”.

The performance will be studied closely by the five permanent members of the UN Security Council and Germany, the so-called P5+1, who are preparing to offer Iran a package of incentives to give up its uranium enrichment programme.

Mr Larijani, viewed by some as a pragmatic hardliner with whom the West could perhaps engage in dialogue, is expected to run against Mr Ahmadinejad in presidential elections next year. The differences between the men on the nuclear issue may well be more a matter of style than substance.

“Larijani's got a certain pragmatic streak but he's not a moderate. He'll want to appear tough and he'll try to present himself as not being Ahmadinejad,” Ali Ansari, a professor in Iranian history at the University of St Andrews in Scotland, said.

Mr Larijani is expected to challenge the President on the economy. Mr Ahmadinejad pledged to give the poor a fairer share of oil wealth, but inflation is above 20 per cent and there is high unemployment.

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