SDLP leader Colum Eastwood has demanded Prime Minister David Cameron withdraw remarks he made describing MPs opposed to air strikes in Syria as 'terrorist sympathisers'.

On Tuesday David Cameron told Conservative MPs not to side with "a bunch of terrorist sympathisers" ahead of Wednesday's crunch vote on Britain launching air strikes against the Islamic State organisation.

“You should not be walking through the lobbies with Jeremy Corbyn and a bunch of terrorist sympathisers,” the PM reportedly told a meeting of the 1922 committee.

The three SDLP MPs are likely to vote against an air strike offensive.

Mr Eastwood said the remarks were appalling and should be withdrawn immediately.

"David Cameron’s remarks describing those opposed to air strikes in Syria as ‘terrorist sympathisers’ are appalling, inaccurate and offensive in the extreme," he said.

"Opposing military action in Syria that will kill innocents and can only feed the evil we all want to defeat is not sympathy with terrorists, it’s part of the lesson we have learned from decades of conflict."

"To describe people like Mark Durkan, Margaret Ritchie and Alasdair McDonnell as ‘terrorist sympathisers’ is absolutely galling. These are people who stood strongly against violence for over forty years at great personal risk while people like David Cameron enjoyed a life of privilege. His comments are totally despicable and he should withdraw them immediately.

"SDLP MPs will proudly walk through the voting lobbies with our colleagues in Labour, the SNP, Plaid Cymru and other parties to oppose military action tomorrow. We will not legitimise the trigger finger of a Prime Minister more concerned with the theatrics of winning a political victory over the Labour Party than the devastation that will rain down on innocents in Raqqa as they are used as human shields by vicious cowards in IS," said Mr Eastwood.

The Prime Minister made the comments as he sought to bolster support ahead of tomorrow's crunch vote on escalating military involvement in Syria.

The Commons decks have been cleared for a 10 hour-plus debate on the case for deploying RAF jets against jihadist targets before the vote at around 10pm.

It is likely that a majority of Northern Ireland's 18 MPs will support air strikes in Syria during the House of Commons vote.

The DUP has announced its eight MPs will support the government's motion for military action.

DUP deputy leader Nigel Dodds said: "Our experience in Northern Ireland has taught us that no other approach can be brought to terrorism."

In a statement, Mr Dodds said his party had sought assurances from the government before promising to support the motion.

The DUP is the joint fourth biggest party at Westminster, with the same number of MPs as the Liberal Democrats.

The Ulster Unionist Party (UUP) has two.

Both UUP MPs have military backgrounds and last week, the party's South Antrim MP Danny Kinahan told the Commons he wanted to see the Islamic State group "totally defeated".