Raids took place on the 20th January by the SFO and the City of London Police, who have confirmed that searches have been carried out at domestic and business addresses in London and the southeast.

No arrests have been made, and nobody has been charged in connection with the investigation.

An SFO spokesman said: 'One of the criteria for the Serious Fraud Office to investigate suspected frauds is £1 million or more. We are currently investigating Sweet & Maxwell, but it is impossible to say at this stage how long this will take'.

A spokesman for Sweet & Maxwell released a statement today, which said: 'The Serious Fraud Office and The City of London Police are investigating an allegation in relation to Sweet & Maxwell. Sweet & Maxwell is co-operating fully to help facilitate this investigation.

'Details of the allegation have not been made known to Sweet & Maxwell but the company believes it concerns certain subscription-related customer refunds. This is an issue the company had been addressing, and at this stage it would be inappropriate to comment further.'