As the elderly population in Scotland continues to swell, questions are being asked about how a Yes vote on independence might shake up the pension prospects of more than a million retirees in the future.

The number of Scots who will need a state pension could rise by more than 500,000 within 25 years, according to the National Records of Scotland, reaching 1.4 million.

Furthermore, research published this week by Prudential suggests one in 10 Scots about to retire this year will rely solely on their state pension.

This helping hand from the government will account for one-third of an average Scottish pensioner's annual income.

Yet research from the Institute of Chartered Accountants in Scotland (Icas) has sparked uncertainty over what might happen, in an independent nation, to state pension entitlements built up prior to such a momentous change.

The 20-page report says: "Responsibility for the 'accrued' entitlement of those of working age living in Scotland to a state pension, and the practicalities of making payments to those who are currently retired, would be a major feature of any formal negotiations between the Scottish Government and the UK Government."

A further complication has been created, ironically, by the coalition government's simplification of the state pension, according to Icas.

The new flat-rate pension of £144 a week is due to be rolled out in April 2016, one month after Scottish independence could be ushered in.

The report adds: "UK-wide state pension reform means that the starting point for developing a Scottish state pension system is uncertain.

"Would the current UK system provide the starting point, or would the proposals for the single-tier state pension add further complexity?"

Ronnie Bowie, senior partner with consultants Hymans Robertson, commented: "If I moved to Scotland five years before I retired, would I get my 35 years of pension entitlement from Westminster and five years from Holyrood? There is no precedent for this in state pensions, it would all come down to negotiations."

He added: "Scotland has more pensioners relative to people of working age than in England. That is expected to get worse, and it means a greater burden on public sector finances.

"Can the Scottish Government tell us what its plans are to deal with that?"

Hymans says local authority pensions are self-funded and need not be affected, but the pensions of civil servants, teachers, health workers and the uniformed services would depend on the Scottish public purse.

The Icas report goes on to ask how Scotland would replicate the Pensions Regulator, which safeguards private pensions as well as workplace schemes.

Furthermore, it points out that Holyrood is yet to confirm whether it will continue with automatic enrolment into pensions at work or introduce other policies to build a badly needed savings culture in Scotland.

It also highlights EU solvency rules, which place strict funding requirements on pension schemes that operate in more than one country. It says the potential impact on some employers "is likely to be substantial", with defined-benefit (or final-salary) schemes particularly affected.

On the other hand, the gradual demise of such schemes is widely known, as employers struggle to afford the generous pension guarantees they entail.

Duncan Glassey, director of Edinburgh-based advisory firm Wealth LLP, suggested it could be a minority of pensioners who would feel the full force of the EU rules in this way.

"Defined-contribution schemes, which now dominate the workplace pension landscape, essentially invest your money in the stock market and your pension income is determined by the performance of equities and bonds in the long term."

He also cast doubt on UK Government warnings that an independent Holyrood would find it "difficult and expensive" to replicate the UK's schemes for protecting savings and pensions, such as the Financial Conduct Authority, Financial Services Compensation Scheme and Pension Protection Fund.

The claims were made in a Treasury report published this week, and were hotly disputed by the Scottish Government.

Mr Glassey said: "There is a pension protection fund for investors at the moment and that won't go away, whatever form it might be in for an independent Scotland. I believe there are ways to negotiate a strong safeguard for people's money."

Whatever the future might hold, there are basic steps Scots can take to maximise their retirement saving.

Julie Russell, head of customer relationships from Standard Life, recommends increasing your pension contributions whenever possible, particularly when you receive a pay rise or finish paying off a loan.

She said: "Remember, with pension plans, the Government contributes whenever you do, by rebating the income tax on your contributions. So if you are a basic-rate tax payer, in most cases for every £4 you save in a pension, the Government adds another £1. And if you're in a workplace scheme, your employer is likely to be topping up your contributions too."