An abandoned border guard hut on the northern side of the border between Northern Ireland and the Republic of Ireland

Britain will impose a hard border on the island of Ireland as it leaves the European Union regardless of its impact, a senior Sinn Fein MP has said.

Pat Doherty, former vice president of the party, told a parliamentary committee there is no such thing as a soft border.

Ireland should not be "naive" about an imminent new frontier and needed to realise Britain had only permanent interests, not permanent friends, he said.

"There is no such thing as a soft border... just soft words," he told Dublin's Oireachtas Joint Committee on the Implementation of the Good Friday Agreement.

"The road the British government is travelling on is going to lead to a hard border on the island of Ireland.

"We are in for a very, very difficult time."

The abstentionist West Tyrone MP said it did not matter that every political party, north and south, bar one or two small factions, was opposed to a 310 mile hard border being reimposed between both parts of the island.

"We should not be naive about the intention of the British government," he said.

"They are going to have a hard border and they do not care in any meaningful way about its impact on Ireland."

Mr Doherty said Theresa May's Government cares only about the "Tory and Brexit vote, mostly in England" and Ireland has a huge job to convince Europe of the depth of the problem.

But he added Europe could "devise special circumstances" for Northern Ireland given that every citizen is entitled under the Good Friday Agreement to be an EU citizen.

Public Spending Minister Paschal Donohoe, who appeared before the committee hearing into the impact of Brexit on the peace deal, said the Irish government needed to look at trade and funding models between Sweden and Norway as well as France and Switzerland.

"We want the current trading relationship between the UK and Ireland to be as close to the current circumstances as possible," he said.

"That is the objective we will have entering negotiations."

Mr Donohoe said the British "have left space" in what relationship it will have with the EU's customs union in the future, which allowed an important area to negotiate a trading arrangement that best suits the needs of the Irish economy.

"Any time I visit any of the border counties I hear very clearly from citizens their concerns on economic stability and freedoms now and in the future," he said.

"I agree that we can not see a return to a hard border because of the destabilising effects it would have on the north and other parts of Ireland."