Workers hoping for a comfortable retirement face a risky future 'at best', a think-tank has warned.

Today's pensioners live far more comfortably than those still in work will when they reach retirement age, according to the Institute for Fiscal Studies (IFS), which has sounded alarm bells about a looming pensions crisis.

Nearly nine in ten middle-earning private sector workers are saving less than 15 per cent of their salary - the amount previously recommended by the Government's Pensions Commission.

Those approaching retirement are also increasingly likely to have higher housing costs, the IFS said.

An increasing number of those in their 50s and 60s who are nearing retirement live in more expensive, privately rented accommodation and are not homeowners.

Experts have warned of pension shortages, with incomes set to drop over the coming decade.

This is because a growing number of people will retire with modern workplace pensions and fewer people have generous defined-benefit pensions - also known as final-salary pensions, which provide a guaranteed income through retirement.

Most workers now save into defined-contribution pensions - a pot of cash that you and your employer pay into every year and to which you can gain access from the age of 55.

However, these are less advantageous and secure than final-salary schemes. 

Savers run the risk of running out of money too soon if they don't manage their income carefully.

The IFS said: 'While current pensioners are still doing well on average... the future looks risky at best for many current workers hoping for a comfortable retirement.'

Paul Johnson, director of the think-tank, said a fresh look at the UK retirement saving system was long overdue.

The IFS has launched a Pensions Review, which will run for two and a half years, assessing future risks and determining the measures that need to be taken.

Mr Johnson said: 'Automatic enrolment has brought millions into workplace pensions, but all too often at much lower rates of saving than the Pensions Commission thought would be needed.

'Most private sector workers are left having to manage considerable risks - not least over how long their retirement will be.'

Labour former chancellor Alistair Darling, who is chairman of the independent charitable foundation Abrdn Financial Fairness Trust, which is working with the IFS for its pensions review, warned many people were saving too little for retirement.

'While today, many pensioners are doing well on average, we need a major review to avoid a future where too many won't have enough to live on in their old age,' he said.

Sangita Chawla, managing director at Standard Life,  said: 'The current pension system is under growing strain with a number of long-term pressures starting to build. 

'As things currently stand many younger and midlife workers are at risk of missing even the Pension and Lifetime Savings Association's minimum standard of living in retirement (see below) with the self employed and those who are likely to be renting in retirement especially vulnerable. 

'This is despite the great strides forward made by auto-enrolment and plans to extend it to cover workers from age 18.

'There are also difficult discussions to be had regarding the scope of the state pension, which is the bedrock of most people’s retirement, at time when the public purse is under huge scrutiny.'

James Jones-Tinsley, a pensions expert at Barnett Waddingham, said: 'It takes a long time for pension saving to show through in pensioners' incomes.

'By its nature, it only becomes evident after a full working life - often several decades. 

'Therefore, if pensioners have been doing well since 2009, this is likely a result of their historical defined benefit pensions, or "final salary schemes", which grant a significant and sustainable income through retirement. 

'It cannot be directly related to the successes or failures of auto-enrolment, which only came to pass in 2010.'

Jones-Tinsley said levels of defined contribution mandatory contributions (see below) remain far too low to offer members a 'decent' pension in retirement. 

He added that the self-employed are already two steps behind employees, because they have no employer contributions to help increase their pensions and there is no auto-enrolment  for them. 

'Many people aren’t in any form of workplace pension scheme; they are relying mainly or solely on the state pension.' 

The IFS says: 'The announcement and introduction of pension freedoms precipitated an enormous decline in annuity purchases, and a smaller rise of pensions in drawdown. A large number of people have withdrawn pension pots in full, particularly those with less than £10,000 in a pot.'