Iran has made a significant breakthrough in its efforts to enrich uranium, the international nuclear watchdog confirmed on Friday as it issued a pessimistic assessment of its future ability to monitor Tehran’s nuclear activities.

As expected, Friday’s report to the UN Security Council and the agency’s board contains no proof that Iran is pursuing a nuclear weapons programme in contravention of its obligations under the nuclear non-proliferation treaty. But it will do little to allay concerns that, contrary to its denials, Iran has such a programme.