David Cameron has said: "If this treaty is still alive, if it is still being discussed and debated anywhere in Europe, then we will give you that referendum.

"We will name the date during the election campaign, we'll hold that referendum straight away and I will lead the campaign for a 'no'.

"Now, if those circumstances change, if the Germans ratify, if the Poles ratify, if the Czechs ratify, if the Irish vote yes to the treaty, then a new set of circumstances [apply] and I will address those at the time."