A working group set up by the regulator has urged pension funds to probe the honesty of their asset managers.
Chris Sier, chairman of the institutional disclosure working group at the Financial Conduct Authority, said pension funds should not trust the information they are given about asset management costs outright.
The FCA had uncovered cases where invoices for investment management expenses were 100 per cent wrong, he said.
He said pension schemes should be asking for a detailed breakdown of the cost of investment and should not take "no" for an answer.
Mr Sier said: "If you ask your asset manager for cost disclosure and they don't do it I would argue they are dishonest."
On the other hand, if they give reasons for why they are not able to disclose the data, schemes should ask themselves whether the provider is the right one for them, he added.
"Having someone to check the detail is really important. Never rely on the information you are given," Mr Sier said.
Indeed, he suggested asset managers may need to be assessed and picked for honesty as a primary characteristic.
The group is working on putting together templates for cost disclosure.
Mr Sier said they would be devised at "atomic level" - granular, but taking into consideration the various needs of pension funds.
This was one of the proposed remedies in the FCA's asset management study 2017, which uncovered a range of failings in the sector, including in price competition.
Mr Sier said the groups's objective was to find agreement on a template for cost disclosure as well as creating better awareness and understanding.
"Not knowing there is a problem in the first place is another," he said.
He added the threat alone of acting on transparency had delivered positive change.
"The threat of transparency has changed the market, the impact is considerable," he said.
For instance, he told the audience consultants to pension scheme LGPS had seen asset managers voluntarily offer a headline cost reduction of 15 per cent, amounting to a cost reduction of £125m per year.
He then asked the audience: "Why are they doing it? Have a think about it."