"All the evidence points in the same direction: that Iran is intent on developing nuclear weapons," Cameron said in his first major speech to parliament since his Conservative-Liberal Coalition took power.
He said that even if Iran were to complete the recently announced agreement with Turkey and Brazil, it would still retain around 50 per cent of its stockpile of low-enriched uranium, said Cameron.
"I believe it is time to ratchet-up that pressure and the timetable is short," he said.
His Conservative-led coalition government had a "clear objective to ensure stronger UN and EU sanctions against Iran."
Measures should include restrictions on trade finance, asset freezing and action against banks holding funds for the regime in Tehran.