Britain and the US have raised fears that Russia has shared nuclear secrets with Iran in return for Tehran supplying Moscow with ballistic missiles to bomb Ukraine.

During their summit in Washington DC on Friday, Keir Starmer and US president Joe Biden acknowledged that the two countries were tightening military cooperation at a time when Iran is in the process of enriching enough uranium to complete its long-held goal to build a nuclear bomb.

British sources indicated that concerns were aired about Iran’s trade for nuclear technology, part of a deepening alliance between Tehran and Moscow.