Government reforms to cap auditors' liability will not improve professional indemnity rates for accountants.
First City partner Vic Knope said insurers' risk exposure would not be materially changed by the use of a liability cap.
For a cap to be commercially effective it would still need to be set a high level, he said. "Insurers' exposures will not change."
Any benefits would mainly be felt by auditors conducting work for FTSE companies, where liabilities can run into billions of pounds, Knope said.
"It should make the risk slightly better."
The liability cap is being proposed in the re-drafting of the Companies Act.
Auditors are concerned that they could be hit by large claims arising from corporate collapses. Failures such as Maxwell, Barings Bank and Polly Peck have hit audit firms hard.
Ernst & Young is currently fighting a £2.5bn negligence claims from Equitable Life.