Iran today sent a defiant signal to the international community by announcing plans to build 10 uranium enrichment plants days after it was condemned by the UN for concealing activities that are feared may be designed to produce an atomic bomb.

Mahmoud Ahmadinejad's government said the plants would be the same size as the main enrichment complex at Natanz, central Iran, and work would begin within two months.

"We have a friendly approach towards the world but at the same time we won't let anyone harm even one iota of the Iranian nation's rights," the president said. The aim was to produce 250-300 tonnes of nuclear fuel a year by using centrifuges with a higher speed.

The announcement seems likely to strengthen the hands of those arguing for sanctions if negotiations do not resume soon. The Foreign Office called the development "a matter of serious concern". The news from Tehran followed Friday's rare display of unanimity by the security council's "big five" – the US, Russia, China, Britain and France – who condemned Iran for concealing an enrichment plant in a mountainside near Qom.

The 25-3 vote by the International Atomic Energy Agency, the UN's nuclear watchdog, was seen as a sign of deepening exasperation over the impasse. Mohammed ElBaradei, the outgoing IAEA chief, warned that talks were at "a dead end".

As a signatory to the nuclear non- proliferation treaty, Iran has the right to generate nuclear power for peaceful purposes, which is what is says it wants to do. But five UN resolutions demand it suspend enrichment and it is refusing to comply.

Nor is Iran any closer to allaying suspicions it is seeking to secretly build a nuclear weapon. It has been asked by the IAEA to discuss evidence of warhead-related research activities but has refused. Having been caught cheating in the past, its repeated denials have little credibility.

In recent weeks, after talks in Geneva and Vienna with the big five and Germany, Iran has seemed to reject a proposal under which most of its uranium would be shipped to France and Russia for processing into fuel for use in civilian reactors.

An arrangement of that kind would give Iran the nuclear fuel it needs but provide guarantees that it was not being diverted for military purposes.

Analysts and officials suggested the Iranian move was more about making gestures than a realistic plan. "This is mostly about presenting two fingers to the world," said one diplomat.

Others also pointed to the president's domestic problems, where he is under pressure from conservatives in parliament, from the supreme leader, Ayatollah Ali Khamenei, and from opposition supporters protesting against the "theft" of last June's election.

"It's bluster," said Sir Richard Dalton, a former British ambassador to Tehran. "Iran can't afford 10 plants the size of Natanz and 500,000 centrifuges."

But the move is likely to galvanise efforts to put together a package of sanctions, perhaps persuading Russia and China to back moves supported by the US, Britain and France.

Israel welcomed Friday's censure by the IAEA but has made clear for months that it reserves the right to take pre-emptive military action if it felt that its own nuclear deterrence were to be challenged by Tehran.

The US warned on Friday that its patience is not unlimited, but doors are being left open in the hope that Iran will somehow re-engage.

Earlier today MPs announced the allocation of $20m for unnamed "progressive" groups to combat what it called US and British "conspiracies." Iran's parliament said the money would be disbursed by a committee including representatives of the ministries of intelligence, foreign affairs and the Revolutionary Guards.