Brooks Macdonald and Psigma Investment Management have both added their names to a list that also includes Quilter and Rathbones.
Those firms earlier this week said they were collaborating on a discretionary management equivalent to the total expense ratio (TER) calculations used in the fund industry.
Andrew Shepherd, joint managing director of Brooks Macdonald, said he would get involved in such a project “in a heartbeat”.
“Producing a TER-equivalent can only help to increase clarity for advisers, and creating a level playing field will benefit both advisers and discretionary managers,” he said.
“The key is to make sure that all discretionary managers are putting the same thing into their calculations, which they are not doing right now.”
Mr Sheppard said all the major discretionary managers would need to sign up for the plans to achieve a critical mass.
“If we get enough of the big players in the industry involved then everyone will have to follow it, because advisers will force them to,” he said.
Frank McGarry, director of business development and marketing at Psigma, said it was a “fantastic” idea and said the more transparency the industry could provide on costs, the better.
He said: “Some people have the view that cost is not as important as what value is added after costs, but if you have not got a consistent way of measuring costs you cannot properly measure value after costs.”