One of Liz Truss's former Treasury ministers today warned that Reform are copying her widely discredited economic plans and cannot be trusted.
Chris Philp took aim at his former boss as he tried to discredit the low-tax, high-spending policies of Nigel Farage's party, which is leading in the polls.
Shadow home secretary Mr Philp was chief secretary to the Treasury when Ms Truss and Chancellor Kwasi Kwarteng introduced her 2022 mini-Budget that sparked chaos in the markets.
When his role in it was raised by broadcasters he admitted that 'mistakes were made', though he stopped short of apologising for it taking place.
He claimed that he had been quietly 'arguing for spending restraint' but 'those warnings were sadly, not listened to'.
Asked if it was time for the Conservatives to think about a more constructive approach to Reform, he told Sunday Morning With Trevor Phillips on Sky News: 'I mean, they're all essentially a protest party.'
'I mean, you just asked about Liz Truss, right; I mean, they're offering populist policies that are essentially Liz Truss on steroids.'
The shadow home secretary's remarks came after shadow chancellor Sir Mel Stride triggered a new row with Ms Truss - who lost her seat at the general election - by distancing them from what happened three years ago.
In a speech on Thursday, shadow chancellor Sir Mel said the party needed to show 'contrition' to restore its economic credibility.
Addressing the legacy of the 2022 mini-budget under Ms Truss's premiership, which spooked the financial markets and led to a spike in mortgage rates, Mr Stride said say: 'For a few weeks, we put at risk the very stability which Conservatives had always said must be carefully protected.'
'The credibility of the UK's economic framework was undermined by spending billions on subsidising energy bills and tax cuts, with no proper plan for how this would be paid for.'
'As a Conservative, of course I want taxes to be as low as possible. But that must be achieved responsibly through fiscal discipline.'
'Back then mistakes were recognised and stability restored within weeks, with the full backing of my party. But the damage to our credibility is not so easily undone.'
'That will take time. And it also requires contrition. So let me be clear: never again will the Conservative Party undermine fiscal credibility by making promises we cannot afford.'
His remarks triggered a spat with Ms Truss, who accused Mr Stride online of having 'kowtowed to the failed Treasury orthodoxy' and being 'set on undermining my plan for growth'.
His address to the Royal Society for Arts, Manufactures and Commerce is the first major attempt by a senior figure of Kemi Badenoch's shadow Cabinet to distance the party from a difficult time in its 14 years in power.
He warned that it would take time for the Conservatives to regain their reputation for 'stability and fiscal security' and called for 'responsible radicalism'.
Taking aim at both Labour and Reform UK, he also accused Chancellor Rachel Reeves of 'fiddling the figures' by changing her definition of national debt.
He also fired a broadside at Nigel Farage, saying his support for measures such as lifting the two-child benefit cap 'doubles down on the ''magic money tree'' we thought had been banished with Jeremy Corbyn'.
Asked by the BBC on Friday whether she would consider throwing former prime minister Ms Truss out of the Conservatives in a symbolic break with her short-lived, turbulent time in No 10, current leader Kemi Badenoch replied: 'Is she still in the party?'
Ms Truss, the former Conservative MP for South West Norfolk, is understood to be a Tory party member still.