Gordon Brown and Alex Salmond have exchanged insults over the future of the NHS.

Brown claimed the SNP were "perpetrating a lie" about protecting the NHS with independence, saying Holyrood already has the power to keep the health service in public hands.

Brown said the nationalists should make way for a Labour government in Scotland if they continue to insist they are "powerless" to protect the NHS without a Yes vote in the independence referendum.

The SNP has argued that the health service north of the border is at risk due to health policies at Westminster, despite the area being devolved to the Scottish Parliament.

Speaking at a campaign event in Clydebank, West Dunbartonshire, Brown said: "I think people are going to come to the conclusion that the change they really want is to have a Scottish Parliament as part of the UK, not the change that the SNP want, which is the chaos of a separate state."

He continued: "The NHS lie of the Scottish National Party has been exposed. The Scottish Parliament can keep the NHS in public hands with its existing powers.

"If the SNP continue to say they are powerless to protect the NHS in Scotland, let them make way for a Labour government in Scotland and we will protect the NHS."

Brown said the Labour Party would never allow the health service to be privatised in Scotland.

"It is the SNP who are perpetrating a lie about what the NHS can and cannot do in Scotland," he said.

"Over these next few hours, you must remind the people in Scotland the NHS has the powers and the Scottish Parliament has the powers to fund the health service, to protect the health service, to stop any privatisation, and to keep the health service in public hands."

Meanwhile, Salmond said claims that Scotland would be forced to cut funding to the NHS to plug a black hole in finances were "absolutely untrue".

The NHS is facing a funding gap of up to £450 million and major changes will be needed to find savings, private documents passed to the BBC suggest.

According to the papers, which were presented to a meeting of health board chief executives and civil servants last month, new obligations are "not fully funded" and the "status quo in terms of service and workforce planning is not an option".

Better Together leader Alistair Darling told BBC Radio Scotland that the First and Deputy First Ministers had been deceiving voters over the future of the NHS.

He said: "Today we learn that Alex Salmond and Nicola Sturgeon have been deceiving us.

"We find that they are planning to cut £450 million from Scotland's health budget, something over which they have total control, and yet they were going to keep this under wraps until after the referendum.

"I find that quite appalling after all the things they have been saying about the health service, all these scare stories and all the time they have known that these cuts were coming along but we weren't going to be told about it until after the polls close."

The funding gap is put at between £400 million and £450 million during the 2015/16 financial year, according to the papers - a level described as "significantly in excess of that previously required".

Options that health boards will have to consider include centralising hospitals and closing services, the papers say.

The documents state: "The status quo and preservation of existing models of care are no longer an option given the pressing challenges we face."

Mr Salmond said cuts claims were "mythical" and pointed to plans passed in the Scottish Parliament earlier this year that the overall budget goes from £11.9 billion to £12.7 billion next year.

He said: "What this paper does is part of the normal planning in the health service.

"It says that we'll need 3.5% efficiencies in order to meet commitments in the rising cost of procedures in the health service.

"In the last six years we have managed 3% and that's all been ploughed back, every single penny of it, into the health service. That's why we have increased funding in real terms."

Scottish Liberal Democrat leader Willie Rennie called on Health Secretary Alex Neil to give "immediate answers" about NHS finances.

He said: "We need immediate answers from the Health Secretary on his £400 million secret NHS cuts plan.

"This would be a devastating cuts agenda which would fundamentally undermine the ability of our NHS. It is unpardonable that this significant news has been kept hidden from voters.

"Despite this meeting taking place in early August, the nationalists proceeded to spread fear about the future of our NHS.

"But they knew all along that the only real risk to our NHS was their independence plans. We need to know who at the top of the nationalist government knew about these plans."

Commenting on the documents, Deputy First Minister Nicola Sturgeon said: "This is a discussion document not a decision document. I'm part of a Government that has protected the revenue budgets of the health service and will continue to strive to do that.

"It's a discussion document written in the context of the status quo, not in the context of independence. The No campaign is jumping on this today, I'm not sure if they realise they are making our case for us because the centre of the case around the NHS is that yes, we've got policy control but we don't have control over our own resources, and as long as we remain at the mercy of Westminster cuts to our overall budget then it gets harder to protect the things that matter.

"What we need to do is marry up the policy control with control over our own resources."