Scottish Labour leader Wendy Alexander clashed with SNP First Minister Alex Salmond today over her calls for an early referendum on independence.

She challenged Mr Salmond to bring forward his planned referendum when he announces his legislative programme next week.

But at First Minister's Questions at the Scottish Parliament, Ms Alexander faced mockery from the SNP leader over her public demands for an early referendum.

Rival parties claim she had been left in an "untenable" position after Gordon Brown failed to endorse her call for an early referendum on independence.

But Ms Alexander has said she has no plans to quit and today she attempted to turn the tables on Mr Salmond.

She said: "The First Minister is the problem when it comes to resolving this issue in the nation's interest.

"The First Minister has a statement next week on his programme for government.

"The question is simply - will he bring forward a referendum Bill in next year's legislative programme next week?"

Mr Salmond shot back: "The answer is, we'll stick to what was laid out in the SNP manifesto on page eight and 15.

"While I would not say Wendy Alexander is the only problem the Labour Party has, I think quite convincingly after the last few days that she is not the answer."

The clashes began with Mr Salmond inviting Ms Alexander "to coin a phrase, bring it on" - a reference to a TV interview last Sunday in which she called for an early referendum.

She told MSPs: "The First Minister has been a nationalist all his political life.

"I'm giving him the opportunity to resolve the issue. Why won't he take it?"

Mr Salmond said he acknowledged the "progress" that the Labour leader had made over the last week.

"She now accepts the right of this Parliament to decide the future in terms of a constitutional referendum put to the people of Scotland," he said.

He told MSPs that Labour backbencher Duncan McNeil had said Labour would not vote down any referendum Bill that came to the Parliament.

"When we bring forward that Bill knowing that the Labour Party will support it, as stated in our manifesto in 2010, we will expect the support of every Labour member in this Parliament," said the First Minister.

"Given the progress that Wendy Alexander has made in the last few days, who knows what side she'll be campaigning on?"

Ms Alexander hit back: "This is far too serious a matter to jest with."

She went on: "We believe that the uncertainty is damaging Scotland.

"I and my colleagues have therefore offered our support to bring this issue forward now.

"We believe that Scotland deserves a choice sooner rather than later.

"The First Minister tells us that over 80% of Scots want a referendum - so why are we still waiting?"

Mr Salmond retorted: "If Wendy Alexander will allow us, I thought we would stick to what is in the SNP manifesto on pages eight and 15.

"Week after week, Wendy Alexander comes and demands that we stick to the SNP manifesto - attacks us for not doing so."

He went on: "Now she's telling us we shouldn't stick to the manifesto and the 2010 date.

"Does she not feel her credibility on keeping manifesto promises is being somewhat damaged by this process?"

Mr Salmond continued: "I agree with Wendy Alexander that this is a serious process - which is why we are engaged in a serious way, through the National Conversation (the Scottish Government-sponsored national debate on the country's future).

"But it is impossible for anyone outside the Labour Party - and I think most people in it - to take the Labour Party seriously after the last few days."

Ms Alexander said CBI Scotland boss Ian MacMillan had said it was time to "lance the boil".

"I have offered Labour's support for an early referendum," said the Labour leader.

"The First Minister has spurned that offer - why won't he bring the Bill on?"

Mr Salmond told her: "I welcome the upsurge in support for a referendum from Ian MacMillan and everyone else."

Labour today closed ranks around the embattled Scottish leader as speculation persisted over her future.

MSP Malcolm Chisholm today insisted her call for an early referendum was right, and that her position was safe.

"It's absolutely safe because she has widespread support, not only within the Labour Party but I believe throughout Scotland," he told BBC Radio Scotland.

He also denied that Gordon Brown had been ambivalent in his support for Ms Alexander.

Tory leader David Cameron accused the Prime Minister of treating the public like "fools" after Mr Brown claimed Ms Alexander had not called for an immediate referendum on Scottish independence.

To the astonishment of opposition MPs, the Prime Minister said: "That is not what she has said," adding that she had simply been trying to expose the "hollowness" of the position of the SNP.

In a later exchange of letters, Mr Cameron recalled that Ms Alexander has said "bring it on", and that she had also said it was time for the SNP to put up or shut up.

But Mr Brown said nobody was seeking referendum legislation at Westminster, and under Scottish Parliament procedures a Bill introduced there would take up to 12 months to complete.

Alex Salmond, whose party has pledged legislation in 2010 for an independence referendum, said last night that Labour had brought him a step closer to his goal of independence.

He also said of Ms Alexander and Gordon Brown: "Either he is misrepresenting her, or she is misrepresenting him, or they are both misrepresenting each other."

But Mr Chisholm, Labour MSP for Edinburgh North and Leith, told the Good Morning Scotland programme Ms Alexander's call for a referendum commanded widespread support.

"What she said was quite simple - she said the SNP should bring the referendum Bill forward in the interests of Scotland," he said.

"The SNP claim to be the party that supports business - why don't they listen to the voices of business and the voices of people throughout Scotland on this issue?"

Ms Alexander has also not ruled out the possibility of Labour bringing forward its own Bill.

It then appeared that such a move could fall foul of Holyrood rules which bar a Bill being brought forward if similar legislation is expected from the government.

Mr Chisholm denied there had been a contradiction in the stance taken by Ms Alexander and Mr Brown, or that Ms Alexander's move had rendered redundant the Calman Commission, which is studying more powers for the Scottish Parliament but not independence.

"There is absolutely no contradiction between what Gordon Brown said about Calman and what Wendy Alexander has been saying about a referendum," he said.

"Of course we need a choice, but we also need to have the Calman Commission to review, and I believe extend, the powers of the Scottish Parliament within the UK."