David Cameron has indicated he will force a referendum on Scottish independence "sooner rather than later" and accused Alex Salmond of damaging the Scottish economy by putting off a vote.

Speaking on the BBC's Andrew Marr programme on Sunday morning, the prime minister said the delay in holding a referendum was causing businesses to hold off investing in the country.

"I think there is a problem," he said. "One is uncertainty about this issue is damaging to Scotland and Scotland's economy. Secondly it's very unfair on the Scottish people themselves, who don't really know when this question is going to be asked."

He added: "I think we owe the Scottish people something that is fair, legal and decisive".

After winning a majority at Holyrood last year, SNP leader and first minister Alex Salmond pledged to hold a referendum on achieving his long-held dream of an independent Scotland before the end of this Parliament.

Salmond is believed to want to hold the poll in 2014, the 700th anniversary of the Battle of Bannockburn which saw the English defeated by the Scots.

But Cameron accused Salmond of putting off the vote for as long as he could because he knew the Scottish people "don't want a full separation".

The prime minister said the United Kingdom was one of the "most successful partnerships in the history of the world" and it would "desperately sad" if it broke up.

According to the Mail on Sunday, Cameron has received legal advice that confirms Scotland can not hold a referendum without the permission of Westminster. It reports he intends to weld that power to force Salmond to bring forward the vote.

The prime minister told the BBC on Sunday the legal position will be set out in the coming days.

Cameron's words were echoed by Lib Dem chief secretary to the Treasury Danny Alexander, a Scot, who told Sky News it would be "totally wrong" to break up the United Kingdom.

"Scotland can not afford for a long period of dithering and delay from Alex Salmond that will cost is growth and jobs," he said.