The Conservatives appear intent on downgrading Britain’s relations with Europe, dismayed European Union diplomats warned on Tuesday, saying the Tories’ stance could create serious tensions between London and Brussels if the party were elected.

In a keynote address on the Conservatives’ foreign policy prospectus, William Hague said his party envisaged forging close relations with the US, the Commonwealth, China and Russia in a bid to promote Britain’s role on the world stage.