Responding to a report by the International Atomic Energy Agency (IAEA), Britain's Foreign Office said it was important to apply more diplomatic pressure on Iran. "We will therefore push hard for further U.N. sanctions in the coming weeks," it said.
The IAEA said earlier that Iran had stymied a U.N. inquiry into whether it had covertly researched how to make an atom bomb while expanding uranium enrichment in defiance of international demands. Iran blamed the IAEA for the impasse.
Britain's Foreign Office said it was the second report in a row that had noted Iran's failure to answer the IAEA's questions about studies with a possible military dimension.
"If Iran genuinely wanted to restore trust, it should have made every effort to resolve these over the summer, and implemented the additional safeguards measures requested," it said in a statement.
It said IAEA chief Mohamed ElBaradei had noted his serious concerns about these issues in May.
"Iran shows contempt for the IAEA by continuing to refuse to rsepond to them," the Foreign Office said.
It said Iran had "failed to provide a clear and satisfactory response" to an offer made by six powers leading diplomatic efforts to persuade it to suspend its enrichment programme.
Western powers accuse Iran of seeking to build nuclear weapons under cover of its nuclear energy programme. Tehran rejects the charge.
"Iran needs to come clean about its past activities and suspend enrichment-related activities. Once that has been achieved we will be able to forge a more productive and positive relationship between Iran and the international community," the British statement said.
