Labour leader Jeremy Corbyn has rejected the backstop

Micheál Martin has urged Sinn Féin to use its "special relationship" with Jeremy Corbyn to convince the Labour leader about the merits of the backstop.

The Fianna Fáil leader was commenting amid growing nationalist concern over Mr Corbyn's rejection of the EU's guarantee to maintain a soft border.

The Labour leader has said the backstop would not feature in any withdrawal deal negotiated by a Labour government.

Mr Corbyn has also faced criticism from south Armagh-born Labour MP Conor McGinn for his "invocation of the union" when opposing the withdrawal agreement.

Strains in relations between the DUP and Theresa May over the backstop have led to speculation that Labour may align itself with Arlene Foster's party in an effort to oust the Tories.

But DUP MP Sammy Wilson said yesterday that the party was not in talks with Labour over a potential no-confidence vote.

"We don't need to be in talks with Labour," he told BBC Radio 5 Live.

"We have made it quite clear that if the prime minister continues to pursue the policy and gets the ability to implement that policy, then we will vote against the government in a vote of no confidence. However she has got to get over the first hurdle, and that is to get this agreement accepted by parliament – I don't believe she is ever going to get over that hurdle."

Mr Corbyn's rejection of the backstop and his recent overtures to the DUP have dismayed many nationalists.

Mr McGinn, the MP for St Helens North, told The Irish News earlier this week that the Labour leader risked alienating nationalists and was jeopardising his party's reputation as "protectors of the Good Friday Agreement".

SDLP leader Colum Eastwood said he was "bewildered" by Mr Corbyn's remarks on the backstop, while the Labour Party Irish Society has written to the party's 257 MPs voicing concern about its leadership's stance.

Last night, following a request from The Irish News for Sinn Féin's response to the Labour leader's remarks, a party spokesman echoed sentiments aired by Mary Lou McDonald earlier this week.

"Regardless of who leads the British government, they will always prioritise British interests first," the spokesman said.

“The catastrophe facing Ireland is a result of a Brexit which originated in Westminster."

The spokesman said Sinn Féin was focused on working with the Dublin government and the EU27.

"We cannot allow Ireland or Irish interests to become collateral damage of infighting in a British Parliament that cares nothing for our economy or our citizens," the spokesman said.

"We must protect the Good Friday Agreement and protect the backstop as our only insurance policy against a hard border in Ireland and the economic catastrophe that would bring."

But the Fianna Fáil leader called on Sinn Féin to use its influence with Mr Corbyn to change his mind.

"One disappointing aspect of the Brexit debate in Britain has been the failure of the main opposition party to recognise the role and value of the backstop, particularly in regard to the protection and potential it offers to Northern Ireland," Mr Martin told The Irish News.

"Sinn Féin has made much of its special relationship with Mr Corbyn since he was elected – I think it’s fair to ask why they are not using that influence in defence of the backstop and the effort to protect the north from a hard Brexit."