An independent Scotland would find it harder to afford the state pension than the UK in its current make-up, experts will warn this week.

The independent Pensions Policy Institute will also predict that Scottish ministers could have to raise taxes or cut spending to plug the shortfall.

Scottish ministers have suggested that independence could allow Scotland to offer a lower state pension age than the rest of the UK. The SNP have pointed to lower life expectancy to suggest that Scots are being short changed to the tune of up to £50,000. But experts from the Institute will warn that the picture on pensions is more complex than it might at first appear.

They will point out that within Scotland parts of the country have higher life expectancies than the rest of the UK.

Also, despite the lower average life expectancy, they will say the Scottish population is "ageing" more rapidly than in the rest of the UK. Deputy First Minister Nicola Sturgeon said that her party had set out proposals for an "affordable, fair and efficient pensions system" in an independent Scotland.

"The fact is that social protection spending, which includes pensions and welfare, is more affordable in Scotland than in the rest of the UK - and has been so for the last five years," she added.

"The challenge of supporting an ageing population comes regardless of the outcome of the referendum. But it is only independence that gives us tools to tackle it."

But the pro-Union parties said that sharing resources with the rest of the UK benefitted Scotland's pensioners.

For the Better Together No campaign, Labour's shadow pensions minister Gregg McClymont said: "Pooling and sharing our resources across the whole of the UK means pensions are more affordable in Scotland."

Willie Rennie, the Scottish Liberal Democrat leader, said: "This is another assessment from independent analysts that shows we can better protect the progress we have made by sticking with the UK.