Image caption David Cameron says a Brexit could mean new Irish border controls or "some sort of checks" as people left Belfast to go to the rest of the UK.

David Cameron has said a vote to leave the European Union risks having to implement checks on people leaving Northern Ireland for other parts of the United Kingdom.

The referendum on the UK membership of the EU will be held on 23 June.

Mr Cameron was speaking at Prime Minister's Questions on Wednesday.

He was asked by the SDLP's Alasdair McDonnell if a so-called Brexit meant a return to border customs posts and checkpoints on the Irish border.

During 30 years of the Troubles security checkpoints were common place on the border between Northern Ireland and the Republic of Ireland.

Mr Cameron replied in a leave scenario there could be new border controls or "some sort of checks" as people left Belfast to go to the rest of the UK.

However 'Leave' campaigner, the DUP's Sammy Wilson, has previously told the BBC he does not believe there would be Irish border controls.

"There's a land border between France and Switzerland and you don't have sealing of the border, so why would Northern Ireland and the Republic of Ireland be any different?"

Meanwhile, the DUP has confirmed it will join with rebel Conservative MPs in opposing the chancellor's plans for a special Brexit budget in the event of a Leave vote in next week's EU referendum.

The party's eight MPs will ally themselves with up to 57 Conservatives in voting against such a budget.