Speaking a day after Iran's nuclear negotiator protested over the West's attitude to Tehran's atomic programme, he said Britain was "very concerned" about Iran's refusal to be frank with the International Atomic Energy Authority Agency (IAEA), the UN's nuclear watchdog.

"We are making a serious offer to Iran for economic, cultural, and scientific co-operation which I think is the way forward," he said in an exchange with lawmakers in the House of Commons.

"But it's not a way forward while they continue to defy not just the UN Security Council but also the (IAEA) which has continuing serious concerns about their programme and the refusal of the Iranian government to come clean about it."

He added: "We must be insistent that a uranium enrichment programme, in defiance not just of the UN Security Council but also of Iran's obligations under the non-proliferation treaty, is a serious danger not just to stability in the Middle East but in the world.

"The Middle East has enough problems without a nuclear arms race," he added.

On Monday Iran's nuclear negotiator Said Jalili sent a protest to EU foreign policy chief Javier Solana over the West's attitude to his country's atomic programme.

In the letter he complained that the West's "approach has harmed the constructive process of negotiations between the two parties," according to a Iranian official, who declined to be named.

The UN Security Council has slapped three rounds of sanctions on Iran for refusing to suspend uranium enrichment, a process which can be used to make the fissile material for a nuclear bomb.

Iran says it has a right to enrich uranium to make nuclear fuel as a signatory to the nuclear Non-Proliferation Treaty (NPT), and denies allegations of seeking atomic weapons.

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