A Sinn Fein councillor has said republicans can't rule out using violence to achieve their aims in future.

The comments by Causeway Coast and Glens representative Tony McCaul have been strongly condemned by his fellow unionist councillors.

The Ulster Unionists said they were "particularly disconcerting" coming so soon after the attempted murder of a prison officer, and the party called on the Sinn Fein leadership to take action against the politician.

Councillor McCaul, who is also a member of the area's Policing and Community Safety Partnership, wrote on Facebook: "Republicans can never rule out any tactic, including violence. I now believe politics is expedient, that view could change if circumstances change."

He made the remarks during a heated exchange on social media on Saturday with Thomas 'Dixie' Elliot, an ex-IRA prisoner from Derry who is a staunch critic of the Sinn Fein leadership.

Councillor McCaul (64) was arrested in Dungiven in November 2014 by detectives investigating paramilitary activity in Co Derry. His council colleague, former Limavady Mayor Sean McGlinchey, was also arrested. Both men were later released unconditionally.

When asked last night by the Belfast Telegraph about his comments on republicans not ruling out the use of violence in future, Mr McCaul said he had been speaking in a historical context.

"It has always been the position that at times republicans have used politics, and at other times violence," he said.

"That's been the reality in history over the centuries. I believe in the peace process but, after my generation, I don't know what will happen."

The Sinn Fein councillor said he didn't support violence and that he had joined the party after the IRA ceasefire "because at that point they were, I believed, the best vehicle to forward my republican views".

He said dissident republicans still believed in using violence, "but I can't speak for those people, I don't know them".

Local Ulster Unionist councillor Darryl Wilson denounced Mr McCaul's "appalling comments" on Facebook and said they were particularly worrying coming so soon after dissident republicans had tried to murder a prison officer.

"It's over to Martin McGuinness and the Sinn Fein leadership to deal with this. Unionists will be watching closely," he said.

DUP councillor Alan McClean said Mr McCaul's remarks on Facebook showed that Sinn Fein was not a normal constitutional party. "Comments about the possibility of republicans returning to violence in future really show Sinn Fein's true colours. No matter how hard Sinn Fein tries, the mask always slips," he added.

TUV councillor Boyd Douglas said: "Sinn Fein are always telling us that the IRA is a thing of the past and they've moved on so people will be deeply disappointed, and alarmed, that some in the party appear to believe that there could be a return to terror in the future."

Speaking after his arrest in 2014, Councillor McCaul told the Derry Journal that police had questioned him about the activities of the 'North Derry Republican Group'.

He described himself as wholly innocent and said his detention by police was "totally unjustified" and distressful.

The PSNI defended their actions. Detective Chief Inspector Una Jennings said: "This is a wide-ranging investigation encompassing numerous incidents, most of which took place over a four-year period dating back to January 2011.

"It has been conducted to the highest professional standards and is subject to all the checks and balances provided by accountability arrangements and the criminal justice system. Police have a duty, to victims, and to the community, to follow all lines of enquiry without fear or favour."

Councillor McCaul told the Belfast Telegraph at the time that he had lodged a complaint with the Police Ombudsman about his arrest but that the Ombudsman had deemed his detention lawful.

Belfast Telegraph