It said the raid had dismantled a suspected organised crime gang believed to be cold-calling and text messaging pension holders across the UK with fraudulent offers that could destroy their retirement plans.

The investigation forms part of a wider cross government multi-agency operation against pension liberation activity, with thousands of people estimated to have released up to £400m into high risk and non-existent investment schemes, many of which are based overseas.

Some of this money has been totally lost to fraudsters, with victims also being hit by significant tax and admin fees.

On Wednesday morning detectives from the National Lead Force for fraud entered a City of London based office housing up to 40 call-operatives, arresting three men and seizing computers and documents. At the same time the investigation team, supported by Police Scotland and SOCA, were arresting two men in Ayr and in Glasgow. Further arrests were made in Cheshire.

The operation was triggered after the National Fraud Intelligence Bureau identified an increasing number of reports to the Action Fraud hotline of people losing their pensions after having been persuaded by the promise of better returns and tax free advances to release their savings.

Commander Steve Head, from the City of London Police, said: “Pension liberation fraud is the new boiler room fraud phenomenon as fraudsters seek to exploit new opportunities thrown up by the changing economic climate. The promise of maximising returns on your pension savings may seem to make good financial sense but the reality is you could be falling into a terrible trap which has the potential to destroy your retirement.

“People should think long and hard before releasing pension funds early and anyone who is cold-called or text messaged with this or any other type of investment opportunity should put the phone down and not reply to the message.”

Pensions minister Steve Webb added: “Pensions liberation fraud is a crime and we along with the police and others across government are cracking down on these schemes.

“The promise of easy money when times are tough is all too tempting, and there are far too many unscrupulous people who will play upon this. If you are offered a deal to unlock your pension, don’t touch it.”