More than £4 million was stolen from 23 law firms by cyber criminals in the last three years, the Solicitors Regulation Authority has said.

In a conference about cyber crime, the regulator said that during visits to 40 law firms to understand the impact of a cyber attack, they found that firms lost an average of £60,000 of client money in every successful attack.

Two firms, it added, had recorded over 100 cyber attacks apiece in one year, while a total of 31 firms were found to have been successfully targeted by cyber criminals between 2016 and 2019.

The SRA found that during their visits to law firms, 11 of the 40 had "inadequate policies" and 10 more had "inadequate controls" to guard against cyber attacks.

Several top law firms have been impersonated in phishing attacks this year, including Clifford Chance and Linklaters, with the latter affected by scams on three separate occasions.

Lawyers have also reported that cyber criminals will impersonate more senior partners at the firm in order to get money out of the firm.

Last month, Bryan Cave Leighton Paisner became the 18th firm to report to the SRA that it had been impersonated by cyber criminals in phishing scams. Firms to have been targeted twice each by scams since the start of 2019 include Mills & Reeve, Watson Farley & Williams and Pennington Manches.