It is estimated that thousands of people have been improperly persuaded to transfer £400m of their savings from legitimate pension schemes, the Times reports.

Warnings were first reported about the risky schemes in 2011, after it was revealed that a number of companies were targeting cash-strapped savers and offering to release cash from their pensions before 55.

Doing so risks a vast tax sting because this counts as an “unauthorised payment”, not to mention a retirement spent in poverty.

Now insurance companies are seeing an increase in the number of pension savers who have asked to transfer their funds to suspicious-looking schemes.

Phoenix, one of Britain’s biggest insurance groups, which owns Pearl Assurance, Britannic and a string of other brands, reported an explosion in such cases.

It says that the number of suspicious transfer requests it had seen has more than trebled from 150 cases over four weeks three months ago to more than 520 recently.

Friends Life says it blocked 482 transfer requests to suspicious schemes in the first five months of this year, compared with only 56 in the whole of 2012. Advisers have warned this could be the next big scandal after PPI.

In May, City of London police raided a call centre in the Square Mile and arrested at least seven people who were allegedly involved in texting and cold-calling people and offering pension liberation schemes.

The Information Commissioner’s Office says the percentage of spam texts about pensions has quadrupled from 2% of messages reported in October last year to 8% in May. The percentage of spam texts reported about PPI have dropped from 65% to 29% over the same period, but remain the most prevalent.

There are fears that the government’s move to automatically enrol all workers into pensions could make it harder to spot liberation scams as there will be a host of small occupational schemes set up that will be hard to vet.