Boris Johnson, the leading candidate to be Britain’s next prime minister, said the next government must reject any EU divorce deal that includes the Irish backstop and that the Irish border issue can be resolved during negotiations for a free trade deal.

Managing the sensitive border between the British province of Northern Ireland and EU member Ireland, and designing an emergency backstop solution to prevent the return of extensive controls after Brexit has proven the most contentious element of divorce negotiations between London and the bloc

"The backstop really represents I am afraid the incoherence at the heart of the strategy that we have been pursuing for the last few years - we have been wanting to come out of the EU supposedly while actually being prepared to stay in the customs union and in full regulatory alignment," Johnson said in a election hustings in Northern Ireland.

"That is tantamount to coming out of the EU, but being run by the EU," he added. "So what I think people in this country want is to come out as the whole of the UK, and solve the issues of the backstop in the context of the FTA (free trade agreement) and use the opportunities that Brexit brings us to do things differently."