A long-standing Sinn Féin member and chairman of a party cumann has made an unprecedented call for Gerry Adams to step down.

Co Tyrone-born Thomas Anthony McNulty, who heads the party's Virginia Mullagh branch in Co Cavan, believes it is time the Sinn Féin president made way for a new leader.

Mr McNulty (67), who served a jail term for IRA membership in Portlaoise alongside Martin McGuinness, told The Irish News that Mr Adams was now hindering the party's electoral expansion in the south.

The veteran republican said he was a committed member of Sinn Féin and paid tribute to Mr Adams's role in the peace process. However, he claimed there was now a "groundswell of opinion" within the party and that many members felt Mr Adams was no longer the best person to lead Sinn Féin.

Mr McNulty, who describes himself as being "in the middle ranks of Sinn Féin", wrote to The Irish News after reading an interview with the Louth TD by Deaglán de Bréadún in the paper on July 8.

He subsequently told this newspaper he was "angered" by Mr Adams's insistence that he was staying on as leader.

"I'm disappointed that this man hasn't been able to see that other people can do a better job than him," he said.

"It's nothing personal but it's time to move over and give a younger, more dynamic person a chance."

Sinn Féin has said Mr Adams received a unanimous endorsement from party members at its last ard fheis.

But according to Mr McNulty, there are a number of candidates on both sides of the border who would make a more effective leader.

He said he supported the northern leadership in 1986 when Mr Adams and his supporters voted to end the party's policy of abstentionism, prompting a split with a faction headed by the late Ruairí Ó Brádaigh.

"Like I believed it was time for change then, I believe it's time for change now," he said.

"On the doors during the election campaign people were saying: 'You'll get a vote from us but not while that man is leader'."

He suggests the former West Belfast MP take on an "ambassadorial role", similar to that given to Joe Cahill, who was made honorary life vice-president of Sinn Féin.

Mr McNulty said the likelihood of another election in the south in the near future made a change of leadership all the more necessary.

"I believe there's a groundswell of opinion from the grassroots to the middle rankings of Sinn Féin, that hasn't been expressed yet but will be very shortly, that the next election should be a different election and that there should be a different leadership there to bring it into the next election."

He claimed there was a "serious amount of support that opinion".

"There may be 10 people in my cumann and I don't think there'd be one person against the letter I have wrote," he said.

Mr McNulty said April's ard fheis, which came less than two weeks before the north's assembly election, was "not the right time" for a debate about the party leadership.

However, he claimed the issue of Mr Adams's leadership would "come to the surface" by the time of next year's conference.

"Instead of this whispering campaign that's going on within the party we need an honest open debate," he said.

Notably, Mr McNulty believes Martin McGuinness should remain as the party's figurehead in the north.

"I think that Martin McGuinness is still a very important cog – I don't think McGuinness can be done without in the north," he said.

Originally from Dungannon, Mr McNulty became involved in the fledgling civil rights movement before joining the Provisional IRA.

He was arrested in the early 1970s for explosives offences and after skipping bail went on the run in the Republic. His experiences are recounted in his book Exiled, which was published in 2013.

A Sinn Féin spokesman said members across Ireland unanimously endorsed Gerry Adams as president at the party's most recent ard fheis three months ago.

The Letter in Full:

Dear Editor,

I have just read your interview with the Sinn Féin President Mr Gerry Adams wherein he stated he has no plans to retire.

This is not good news for Sinn Féin. Gerry Adams should have plans to retire from the leader of the Sinn Féin party.

I was at the Sinn Féin Ard Fheis in 1986 when the then leadership of Sinn Féin was voted out and Mr Adams voted in as leader.I supported that transition of leadership because I knew that the years ahead needed the leadership of the northern men and women under Mr Adams to steer the republican movement from conflict to peace.

This has now been successfully achieved, due in no small measure to Mr Adams and his team at the top of Sinn Féin party.A great debt of gratitude is due to Mr Adams for the fact we now have peace on the island of Ireland.

But just as there was a time for change in 1986, there is a time for change again in 2016. Sammy Davis Junior once famously said that one of the great secrets of life was "knowing when to get on the stage, and knowing when to get off it".

I believe the time has come for Mr Adams to get off it.

Mr Thomas Anthony McNulty

Chairman of Virginia Mullagh Sinn Féin Cumann, Co Cavan.