British Prime Minister Theresa May told members of her government on Wednesday that they would have to deliver Brexit, ruling out any second referendum or any attempt to stay in the European Union by the "back door".

"We must continue to be very clear that 'Brexit means Brexit', that we're going to make a success of it," May told her cabinet of ministers, according to a statement.

"That means there's no second referendum; no attempts to sort of stay in the EU by the back door; that we're actually going to deliver on this."