The party’s leader in Scotland, Tavish Scott, said that over four years the SNP administration’s "hand-outs" would see rich families better off.

Mr Scott said SNP policies of freezing council tax, providing free prescriptions, free schools meals and the abolition of tolls on the Forth Road Bridge and the Tay Bridge would cost £950 million.

It would mean a two-child family on an income of £15,000 a year, which he said was the income of at least 40% of Scottish households, would only be £6 better off over a year.

The same family on an income of £100,000 would be £802 better off over a year, Mr Scott claimed.

He told the party’s annual conference in Bournemouth: "Over four years the SNP will have spent £950 million on a set of distorted priorities and hand-outs that give more to the rich than to the poor.

"This is what you find. If you have two children and earn £100,000 then you will have gained £802 per year from the SNP.

"But if you have two children and you earn £15,000 then you will have gained just six pounds and seven pence.

"So that’s enough for champagne and lobster every night for the rich but a fish supper for the poor.

"So I mean it when I say that in Scotland, the only party at the general election for a fairer society will be the Liberal Democrats."

Mr Scott ridiculed Prime Minister Gordon Brown as the "Caped Crusader of Kirkcaldy" who had only succeeded in destroying banking in Scotland and allowing creeping centralisation.

He also claimed the approach of the SNP was one of wanting ever more centralisation: "Centralised government - Edinburgh knows best - that’s the SNP approach. It won’t wash and we will oppose it." Instead there was "a better way, Liberal way" that "trusts people, gives decisions back, puts local people in charge."

Mr Scott said a Liberal Democrat administration would cut tax loopholes and use the money to cut taxes for the lower paid. The family he referred to on £15,000 would be better off by £700, while "millions" of others would pay no tax.

"That’s our commitment to a fairer society where people get their fair share. That’s the difference we will make."

Scottish Liberal Democrat leader Tavish Scott today said a referendum on independence was an "absolute irrelevance" to the people of Scotland.

Asked about the stance Kevin Lang, Mr Scott told the BBC: "I remember what it's like to be a young, thrusting, energetic parliamentary candidate and you were desperate to get your face on the television, so I can well understand the need to say something which commentators and television reporters are very keen to talk about, but I don't really think the people are."

He told Politics Show Scotland: "There will be of course some discussion, as there is in every party.

"What I think is particularly important at this time is that we focus on the things that matter to people.

"I have never been persuaded that people in Scotland at the moment, or at any time, care about independence above everything else.

"Do they really want to debate the embassies that we'd have to locate round the world?

"Do they really want a debate about a separate Scottish Army when our troops are in Afghanistan. How would we work that one out?"

Mr Scott insisted parties should be focused on getting people back into work.

He told the programme: "There could be a lost generation of Scots, we estimate - young graduates, college leavers and school leavers - out of work.

"It could be as bad as the 1980s. That's the kind of thing that we need to be dealing with, that's the kind of issue that our budget in Scotland should concentrate on.

"If we can agree to concentrate on that, rather than what I think is an absolute irrelevance - certainly for those young people potentially out of work - I think we'd be a better Parliament and we'd be a better country as well."

The SNP said the Scottish Liberal Democrats were "all over the place" on the referendum issue under Mr Scott's leadership.

Nationalist MSP Dr Alasdair Allan said: "The people of Scotland deserve the right to decide the constitutional future of the nation and clearly that opinion is widely held throughout the LibDems.

"We already know that a majority of Lib Dem voters support a referendum.

"Under Tavish Scott's leadership the Lib Dems are all over the place on the issue. Earlier this year we had John Farquhar Munro supporting a similar call by Paddy Ashdown for a referendum."

He added: "Tavish Scott now has to decide where he wants to take his party. His inability to lead his party on this issue is showing.

"It's becoming obvious that standing in the way of the right of the people of Scotland to decide their constitutional future is unpopular."