The trading watchdog will announce findings tomorrow from its probe to make sure that millions of new pension savers do not sink their money into rip-off schemes.
The Office of Fair Trading has been carrying out a study into the £275 billion defined contribution (DC) workplace pensions market, to look at whether such schemes offer value for money, if there is enough pressure on providers to keep their charges low and what size of pension pot savers are likely to end up with at retirement.
The size of the sector is set for rapid growth over the next five years, as up to eight million people are automatically placed into a scheme by their employer as part of Government efforts to get people saving more for their later years.
There has been speculation that the OFT could call for charges to be capped at a certain level so that savers can be confident they are not paying over the odds.
The Government has previously said that it plans to launch a consultation in the near future into introducing caps so that workers do not see their savings gobbled up by hidden costs.
A Department for Work and Pensions spokeswoman said the Government is working to tackle "high and inappropriate pension charges".
She said : "We're helping people save more for their retirement but we want to protect consumers."
The OFT could in theory refer the matter to the Competition Commission, which has powers to shake up whole markets. It recently made a referral to the Commission following a similar investigation into payday lenders.
In a progress report during its pensions investigation, the OFT also raised concerns about firms ramping up annual management charges for workers who change jobs but leave money in their old pension scheme.
Pension charges were also found to be hard to compare in some cases because providers do not present them consistently .
Workers aged between 22 and the state pension age who are not members of a workplace pension are being signed up to one under the Government's plans to head off a looming retirement savings crisis.
Auto enrolment started with larger firms and early indications have shown the scheme to be a success, with nine out of 10 people who have been put into a pension scheme so far staying in.
But f ears have been raised that many people will have little previous experience of pensions and there is a danger that smaller employers in particular could bring investors into schemes which do not represent a good deal.
Tom McPhail, head of pensions research at financial services firm Hargreaves Lansdown, said further concerns are likely to be raised about how easy it is to compare costs.
He said: "Employers are selecting pensions on behalf of their employees. Do employers understand the charges on their scheme and whether they are good value? How do they compare one scheme with another?"
The OFT said previously it was worried that several smaller schemes may ''not have a realistic prospect'' of growing large enough to generate value for those enrolled into them.
Pensions expert and former government adviser Ros Altmann said that the likelihood that a cap will be proposed for the charges on UK pensions, probably at around 1%, raises several issues.
She said: "It is vital to be clear which charges are covered by the cap. Currently, there is a confusing array of cost measures."
Dr Altmann also urged the Government to look again at the charging structure for Nest, the pension scheme designed to be a "low-cost" option to fill gaps in the existing system.
She said: "Any worker who does not stay in the Nest scheme for many years will be at risk of paying much higher charges in Nest than in other schemes, and possibly even more than the 1% cap that might be imposed."
Moves have been taking place within the pensions industry to encourage greater transparency and build confidence in retirement saving and the OFT has been discussing possible action with the Government and regulators.