By Alex Stevenson Follow @alex__stevenson

Scottish nationalists should have the "courage of their convictions" and accept an independence referendum sooner rather than later, Nick Clegg has said.

The deputy prime minister hit out at the Scottish National party (SNP) for "falsely characterising" the nature of the independence debate as the standoff between Holyrood and Westminster over the terms of the coming vote continues.

"The Scottish administration should have the courage of its convictions," Mr Clegg told the Lords' constitution committee in an evidence session this morning.

"For the life of me I can't understand why not they're approaching the great moment when they can put it to the Scottish people they want to obfuscate and confuse - suggesting they're not quite as confident in their own case that I'd have thought they might be."

Alex Salmond's party wants the vote to take place in autumn 2014 and is keen on the idea of a third 'devo-max' option on the ballot paper.

London wants the referendum to take place next year and believes voters should only be offered a 'yes-no' option.

Mr Clegg said the Liberal Democrats preferred a version of "home rule", currently being investigated by former leader Sir Menzies Campbell, but that the coalition's priority was a referendum which is clear, fair, decisive and legal.

"Where the debate has become falsely polarised at the moment - I think some people have an interest in falsely characterising the two options - is by saying the only choice is between complete independence and the status quo," he added.

"That is not actually what is at stake. What is at stake is either this great step into the unknown, of Scotland wrenching itself apart from the UK, and a further process which is a dynamic, ongoing process of greater powers to Scotland.

"Devolution is not a tablet of stone, it is a process."

Mr Clegg resumed his offensive against the SNP when he questioned the limited nature of its detailed proposals on the implications of independence would mean for the UK and Scotland.

Raising issues including currency, defence bases and taxation, he said: "I'd have thought, call me naive, if you're a party with the sole purpose of independence of Scotland you'd have done a bit of homework about what independence actually means."

The deputy prime minister was forced to share a platform with SNP leader Alex Salmond last month, after Mr Salmond had hit out at "bullying and hectoring" from London.

Then Mr Clegg had told the Scottish first minister: "Don't be so jumpy."