Almost one in three of people with a final salary pension will be lured out of it by the Chancellor's promise of being able to convert money purchase pensions into cash from next April, according to Glasgow-based company pensions specialist Hymans Robertson.

It is effectively predicting a mass exodus over the next decade from the schemes hitherto seen as the gold standard.

Consultancy firm Towers Watson said already nearly 10% of employees approaching retirement are interested in exchanging most or all of their final salary pension for a pot they can dip into as they wish. A further 35% would be interested in exchanging half or less of their pension.

Will Aitken, senior consultant at Towers Watson, said: "Prior to the Budget, hardly anyone was interested in exchanging their final salary pension, which was often deemed to be more generous and more secure. Transfers will now become a mainstream choice which pension schemes need to cater for.

"We're now seeing DB [defined benefits, such as final salary] schemes considering whether to include transfer values on all pension statements so members approaching retirement can clearly see what their choices are."

In an attempt to stop people making under-informed and potentially damaging decisions to switch, the Government has said people must consult a regulated adviser. Some providers, including Fidelity, will only accept transfers backed by an adviser. But even with money purchase pensions, where a defined pot is created, cashing it in will be far from simple.

In fact, the Chancellor's latest tweak to the reforms risks impoverishing people in retirement and triggering the biggest ever mis-­selling scandal, industry critics have warned.

George Osborne and his Coalition partner, Pensions Minister Steve Webb, took the last set of brakes off pensions recently by saying retirement pots could be used "like bank accounts". From next April, over-55s will be able to draw down their pension pots in slices, each one 25% tax-free, in a series of "uncrystallised funds pension lumps sums".

In the March Budget, when the pensions liberation bombshell was dropped, it was envisaged that retirees would have an 18-month window in which to convert their pot into cash, with all the tax concession at once. But for many with valuable pots, that would have meant having to park much of it in a drawdown plan to minimise their income tax bill in any one year, prompting worries about rules and charges.

According to Webb, the new, improved state pension will ensure that people who do spend all their savings will have a better safety net than in the past.

But the pensions industry, which is already facing significant upheaval, was quick to warn that the latest loosing of the chains was a step too far,

Tom McPhail at Hargreaves Lansdown said: "At present there are precious few regulatory controls around the non-advised sale of retirement incomes. In fact, it appears that the Treasury is intent on abolishing even the notion of a sales process at retirement, as investors will be able to dip into their pots at will.

"Without regulatory oversight, when investors do run out of money, and some will, there will be no accountability for this system failure. The Chancellor appears to be creating the perfect environment for a mis-selling scandal."

Otto Thoresen, director-general of the Association of British Insurers, said: "The risk to savers of making decisions without the necessary information, or the potential for scammers to become active in this market, is clear. But the prospects of the Government's guidance guarantee being able to cover the gap, or the FCA being able to develop appropriate safeguards in time for next April, are virtually nil."

And Kate Smith, regulatory strategy manager at Edinburgh-based insurer Aegon, said: "As soon as people start to withdraw sums above the 25% tax-free cash it potentially starts to limit future pension savings, as the amount they can put into a pension each year and receive tax relief on reduces from £40,000 to £10,000."

Insurers reeling from the 30% drop in annuity sales since the Budget are now threatened with a drop in demand for the new flexible access drawdown products they are, in many cases, still designing.

Smith said: "For those with small pension pots, taking lump sums and adding them to a bank or savings account may make sense, but for many the new flexi-access products will allow them to manage their income and invest their capital may make more sense.

"People need to remember that from age 55, they can expect to live another 30 years. Even for those with the largest pension pots, this is a long time and there's a real danger that those who make large cash withdrawal in early retirement may outlive their savings unless they're managed carefully."