European Agriculture and Rural Development Commissioner-designate Phil Hogan of Ireland speaks before the European Parliament's Committee on Agriculture and Rural Development at the EU Parliament in Brussels October 2, 2014. REUTERS/Francois Lenoir

DUBLIN (Reuters) - The return of a “hard border” between Northern Ireland and the Irish Republic looks inevitable if Britain leaves the European Union’s single market, Ireland’s European Union Commissioner, farm chief Phil Hogan, was quoted as saying on Monday.

Northern Ireland, a British province, will represent the only land frontier between Britain and the EU once it leaves. Leaders in London, Dublin and Belfast have said they want to avoid a hard border, with customs checks and border posts.

The Irish Independent newspaper quoted Hogan as saying that if the United Kingdom leaves the EU Single Market, then a hard border, involving potential identity controls and customs tariffs, looked inevitable.

He added, however, that he hoped the EU may be able to persuade London on a common position for the island of Ireland, to avoid such measures and preserve a common travel area between the two countries that predates their entry into the EU in 1972.

“Clearly, Brexit is a mess and getting messier,” Agriculture Commissioner Hogan, a former Irish government minister and close ally of Prime Minister Enda Kenny, told the newspaper.

Britain will by definition leave the bloc’s single market in which goods and services trade tariff-free once it leaves the EU, and exit talks expected to begin by the end of March will determine what level of access it gets to it afterwards.

Britain’s pound slid almost 1 percent against both the dollar and the euro in early London trading after weekend comments from Prime Minister Theresa May that she was not interested in keeping “bits of membership”.

May said she instead wanted a bespoke deal with the rest of Europe. EU officials say Britain cannot have access to its single market of 500 million consumers without accepting the principle of free movement.

Given the countries’ close trading links, neighboring Ireland is widely considered the European Union economy most at risk from Britain’s decision to quit the bloc.