The Solicitors Regulation Authority says it is receiving four reports a month of law firms being tricked into giving bank details to fraudsters in so-called ‘Friday afternoon scams’.

The regulator said it continues to get regular reports of scammers stealing from firms despite repeated warnings not to disclose sensitive details.

Criminals tend to target conveyancing firms with large amounts of money in client accounts and are increasingly sophisticated in how they persuade people to release information.

Internet scammers have been known to gain access to a firm’s online systems when malicious software is downloaded from unsolicited email communications. The perpetrators can intercept emails between firms and replace them with their own in an attempt to hijack money from client accounts.

On two occasions these email intercepts have been followed by telephone calls from the fraudsters pretending to be from the bank’s counter-fraud team.

On other occasions, law firms have been called and asked for verification of a specific electronic transaction, with callers stating they suspect fraudulent transactions have been set up. The scammer then asks the firm to confirm their online security information.

In November, the SRA revealed that four firms had collectively had £2m taken from their accounts after falling victim to these schemes.

At the time, Robert Loughlin, SRA executive director of operations, said: ‘These scammers are very active and convincing. They are highly sophisticated in their approach and therefore very capable of duping many people.’

Firms are advised to independently validate callers by contacting somebody they already know at the bank, preferably using a separate telephone line, for example a mobile. There have been examples of scammers keeping the line open to intercept any follow-on call to check.

Angus Ogg, senior professional indemnity underwriter at Elite Insurance, said two law firm clients had fallen victim to scams either side of Christmas.

On both occasions, senior figures in the high street firms were persuaded to give bank details and each saw around £500,000 cleared from client accounts. Ogg said the pattern appears to suggest that fraudsters target times when they know money will be available.

‘We’re not the only ones who have picked up these claims,’ he said.

‘We know of other insurers whose solicitor clients have suffered the same fate. It’s the Friday afternoon scam – they do it at that time because that’s when conveyancing transactions are completed. The firms come back on Monday and there’s nothing left in the account.’