Britain will next week warn Nato allies in Europe that they must pay their "fair share" on defence amid fears that Donald Trump will withdraw US support if they fail to do so.

Sir Michael Fallon, the Defence Secretary, will on Monday use a Brussels summit tell his European counterparts that they must abandon plans for an EU army and back Nato.

It comes after Mr Trump criticised Nato members during the US election campaign for failing to meet their obligation to spend 2 per cent of national income on defence during the election campaign.

He suggested that under his Presidency the US may refuse to come to the aid of Nato allies unless they “pay their bills” and “fulfil their obligations to us”.

The US last year funded 72 per cent of the alliance’s expenditure and is one of only five of the 28 members to meet the spending commitment. Britain also meets the target.