The Government is ordering pension fund managers to come clean about hidden costs which can wipe tens of thousands of pounds off the value of retirement pots.
Pensions minister Steve Webb said transparency in workplace defined contribution schemes was crucial so people could make good financial decisions.
The Office of Fair Trading (OFT) warned last year that there was " insufficient visibility and comparability of charges" to ensure that competition in the market was fully effective.
In a written statement to MPs, Mr Webb said in future ministers would be under a statutory obligation to create rules to ensure transaction costs were more open. An amendment will be introduced to the Pensions Bill in the House of Lords on Wednesday.
"Transparency of costs and charges is fundamental for good scheme governance and to enabling comparison between schemes," Mr Webb said.
"Requiring increased transparency is the latest step in the wider Government programme to see fair charges for people who are automatically enrolled into workplace pensions."
The announcement on transparency has apparently been brought forward to avoid a damaging Lords revolt led by former chancellor Lord Lawson.
Speaking during debate on the Pensions Bill last month Lord Lawson said: "I n a competitive market, compulsory disclosure will go a very long way towards removing the mischief."
Mr Webb also insisted he would "see through" proposals for a cap on fund charges - expected to be around 0.75% a year.
"Last year, we consulted on whether to cap charges in the default funds of schemes used for automatic enrolment, and the Government remains committed to seeing this policy through during the life of this Parliament," he said.
Small variations in charges can make huge differences over time to the eventual size of the pension pot that someone ends up with.
The Government has said someone who saves £100 a month over a typical working lifetime of 46 years could lose almost £170,000 from their pension pot with a 1% charge and over £230,000 with a 1.5% charge.