Chancellor Philip Hammond has been pressed on whether the Brexit withdrawal agreement will include an EU proposal to keep Northern Ireland tied to its customs union and single market.

The proposal, a back-up plan to avoid a hard border between Northern Ireland and the Irish Republic in the absence of a free trade deal, is opposed by the UK government.

But the DUP suspects a reference to it could be included in the final withdrawal agreement, despite the prime minister telling them she could not accept any circumstances in which it would come into force.

Mr Hammond told the BBC the government "will not do anything that puts our union at risk" but did not directly rule out such a "backstop" could be included in the agreement.