Media playback is unsupported on your device Media caption Gerry Adams said the referendum was a "matter for the people of Scotland"

The Sinn Féin president has claimed that the United Kingdom as a union of four countries is hanging by a thread.

Gerry Adams made his comments as Prime Minister David Cameron urged the people of Scotland to vote to stay in the UK in September's independence referendum.

Mr Adams said that the "so-called United Kingdom" was held together by a thread that could be unravelled by referenda in Scotland and Ireland.

He was speaking on BBC Radio Ulster's Inside Politics programme.

Mr Adams said that the referendum vote was a "matter for the people of Scotland", and added that his party had "stayed out of the debate".

His comments came as Sinn Féin activists gathered for the party's annual conference (ard fheis) in Wexford.

Mr Cameron used a speech in England to campaign against Scottish independence.

Knock-on effects

Speaking at the Olympic stadium in London, he said: "This speech is addressed not to the people of Scotland, but to the people of England, Wales and Northern Ireland. We would be deeply diminished without Scotland."

Ahead of the 18 September vote a number of unionists from Northern Ireland have indicated they would be prepared to travel to Scotland to campaign against independence.

It is clear the vote worries unionists, who are concerned about the knock-on effects for Northern Ireland.

Speaking in Westminster earlier this week, DUP MP Ian Paisley Jr said that a "division in this wonderful union" would have "an unnerving and unsettling effect".

The North Antrim MP added that a 'yes' vote would "get the tails up of Irish republicans", and would "drive another wedge into the hearts and souls of people in Ulster".

About four million people over the age of 16 and living in Scotland will be able to take part in the referendum.

Meanwhile, Deputy First Minister Martin McGuinness told conference delegates on Friday that agreement should be reached now on flags, parades and the past.

Mr McGuinness said he believed "sensible people within unionism" needed to "break free of the naysayers, and lead from the front".

Ard fheis delegates also heard party chairman Declan Kearney call for an end to personal criticism of Mr Adams.

"Let me say this: the relentless campaign of vilification against the republican leadership, and specifically Gerry Adams in this state, is a disgrace, and should stop immediately," he said.

Inside Politics is repeated on Sunday 9 February at 12:03 GMT, and is available to listen to on the BBC's iPlayer.