Damian McPhun, partner at Beale and Company Solicitors, said the Fos was the most difficult element of any PI cover because "the Fos can do what they want effectively".
He added: "PI insurers simply don't know what is going to happen. They are very nervous and it is the biggest reason why there aren't more PI insurers in the market.
"Advisers are thinking about leaving the DB market because of this. There’s a number of our clients who could leave partly because of the Fos limit, but also because of the difficulty of getting cover for DB transfers, who are simply saying 'we're not going to do it, it's not worth the hassle'.
"You have this perfect storm of pension freedoms coming in, people wanting to take advice on it, but the regulator and the insurance market, because of the regulator, making it very difficult for advice firms to give advice on that."