The company wants to see an independent commission set up to review pension tax reliefs to avoid constant change and damaging cuts in the future.

Earlier this week at the CISI annual Financial Planning Conference in Wales, ex-pensions minister Sir Steve Webb predicted there was a strong likelihood the Chancellor will have to cut pension tax reliefs in his November Budget, or soon after, to make up for revenue shortfalls. Giving a keynote speech, he predicted that the £40,000 annual allowance could be the first target in the Chancellor's firing line. He said this could be reduced to as low as £30,000.

The lifetime allowance, currently £1m, could also be cut, he said as the Chancellor faces up to a November Budget where he will need to make up lost revenue from failed tax measures earlier in the year.

AJ Bell’s warning comes with news that personal pension contributions hit a record high in 2015/16 with 9m people contributing £24.3 billion. AJ Bell says that while this exceeds the pre-financial crisis high of £20.9 billion in 2007/08 the average annual contribution per individual has fallen from a peak of £3,690 in 2011/12 to £2,690 in 2015/16.

Because of this, it says net tax relief – which takes into account tax taken from pensions in payment – was £24.8billion (2014/15: £21.8billion)

Tom Selby, senior analyst at AJ Bell, said: “There has already been speculation that Chancellor Philip Hammond will take the axe to pension tax relief in his first post-election Budget, and numbers such as these will inevitably add fuel to the fire. But it is vital that the embryonic savings culture being nurtured in the UK is not wrecked by a Treasury desperate to raise cash ahead of Brexit.

“Pensions have suffered from years of chopping and changing of tax incentives. We have reached a point in time where the political sting needs to be taken out of the pension tax debate through the establishment of an independent commission. Such a commission could propose reforms based on the long-term interests of savers and in the process rid us of the some of the horrific, unnecessary complexity that exists in the current system.”

Mr Selby said the Treasury’s pension tax relief bill is rising because automatic enrolment has been successful in boosting the number of people saving for retirement in the UK.

While the net annual bill of almost £25billion for tax relief is a “scary number”, he pointed out that the average savings levels per person remains down compared to the peak of 2011/12.