British MPs have criticised the Taoiseach's intervention in the EU referendum debate, condemning as "scaremongering" his warning about the potentially negative impact of a Brexit on the peace process in the North.

The chairman of the House of Commons Northern Ireland Affairs committee, Conservative MP Laurence Robertson, described the Taoiseach's remarks as "offensive".

DUP MP Ian Paisley said it could be counterproductive for the Irish Government "to try to influence in any way the voting intentions of people in the United Kingdom on this issue".

The committee was hearing evidence from Ireland's ambassador to London Dan Mulhall on the consequences for Northern Ireland of Britain leaving the EU.

Mr Mulhall insisted that the Taoiseach, along with other Ministers and officials, acknowledged that the referendum was a matter for the people of the United Kingdom to decide. But he said that as a fellow EU member-state and co-guarantor with Britain of the peace process, the Government was justified in making its views known.

“Our role is to assess the consequences for Ireland, and in particular for our ties with Britain and for north-south relations in Ireland,” he said.

Economic impact

Mr Mulhall said that Ireland’s concerns focused on the economic and trade impact of Britain leaving the EU, along with its consequences for Northern Ireland and the border. “Our open border is the biggest symbol of all, perhaps, of normalising and developing the full potential of north-south relations. The fact is that no-one can be 100 per cent certain about what the impact on the border will be if the UK leaves the EU. That is something which would form part of the terms of a UK exit, something we will have to negotiate with all EU member states,” he said.

Earlier, the committee heard from Tom Arnold, director general of the Institute for International and European affairs and John McGrane, director general of the British Irish Chamber of Commerce. Mr Arnold, who is also chairman of The Irish Times Trust, told the committee that there was an urgent need for a detailed, authoritative study of the impact of Brexit on Northern Ireland's agri-food industry.

He said that a study of the impact of Brexit on the Irish agri-food industry had concluded that it would be unambiguously negative. “There are similarities between the Irish and Northern Irish Agri-food sectors in terms of their relative weight in the overall economy, their dependence on exports to the EU, and the degree to which CAP income supports represent a very high proportion of net farm income,” he said.

Mr McGrane said that, although trade between Ireland and the UK would undoubtedly continue after a Brexit, it was unclear under what conditions that trade would be conducted.