Andy Burnham blamed Thatcher for Britain's problems today as he tried to get his by-election bid going with a 'vibes' video.
Nearly 36 years after she left No10, the Manchester Mayor said the Tory doyenne was responsible for 'a lot' of the issues confronting the country.
The claim came as Mr Burnham struggles to explain what he would do if he succeeds in getting into the Commons and ousting Keir Starmer.
The former minister under Tony Blair and Gordon Brown has already U-turned by insisting he is not proposing rejoining the EU, or ripping up the Government's fiscal rules - something that had alarmed markets.
Critics have also accused him of watering down his commitment to a proportional representation - PR - voting system.
Instead Mr Burnham has suggested he would like MPs to be elected using the supplementary vote method, and kicked the issue down the road by admitting it would need to be in a manifesto first.
Andy Burnham blamed Thatcher for Britain's problems today as he tried to get his by-election bid going with a 'vibes' video
Mr Burnham is struggling to explain what he would do if he succeeds in getting into the Commons and ousting Keir Starmer
Polling by YouGov suggested Mr Burnham would be Labour members' preferred candidate for leader, winning in a run-off against Sir Keir
Nearly 36 years after she left No10, the Manchester Mayor said the Tory doyenne was responsible for 'a lot' of the issues confronting the country
Other policies floated by the mayor in the past include increasing the top rate of tax to 50p, while he has praised Gordon Brown's disastrous 10p tax rate.
He has also suggested that 'wealth' would be shifted from the South to the North of England.
The vagueness of the mayor's approach has come to the fore as the Makerfield by-election contest ramps up.
Labour has plunged into civil war following disastrous local elections, with more than 100 MPs demanding Sir Keir's resignation - although as yet there is no formal challenge.
Mr Burnham used a slick campaign video overnight to insist he was motivated by the need to 'change Labour'.
In the video, soundtracked by a series of Manchester bands including Elbow, James and Oasis, Mr Burnham said he wanted 'a new path for Britain'.
'Some say this by-election is unnecessary. I say it's the most consequential of our lives,' he said.
'I don't take anything for granted and I'm ready to accept the consequences of whatever choice people make.'
He said: 'Manchesterism is the end of neoliberalism, the end of trickle-down economics that has left out places like Makerfield.
'Make no mistake, that means a new path for Britain.'
The mayor also reposted an attempt to explain his 'Manchesterism' platform by former Guardian journalist Shiv Malik, who termed it 'the Mutual Future'.
The tweet said Mr Burnham wanted 'self-sufficient regions rooting capital in their community to protect them against the tumult of globalisation'.
'It's about ensuring the fundamentals of an economy- energy, transport, water and even housing - can stop being a drag on people's pay packets and the cost of business.
'That frees up people to innovate, spend, save for a better future, and take risks...
'What it isn't is status quo Neo-liberalism or Fabian style nationalisation. Which is why everyone is struggling to name it. It's the Mutual Future.'
Responding to jibes on X that Baroness Thatcher was in power four decades ago and he was part of a Labour Government between 1997 and 2010, Mr Burnham said: 'You've clearly got no idea how much people here are struggling. And, yes, a lot of it can be traced back to Margaret Thatcher.'
The by-election was triggered by former minister Josh Simons quitting to make way for Mr Burnham.
If he is successful there will have to be an election for Greater Manchester Mayor, with costs running into millions of pounds.
Reform UK is targeting Makerfield and has already said the 'expensive by-election is all about (Mr Burnham's) own personal ambition' rather than the best interests of the constituency.
Mr Burnham has sought to reassure voters in the Leave-supporting constituency that he is not seeking to rejoin the EU – something he said last year he would like to see happen in his lifetime.
Sir Keir has insisted he will not set out a timetable for his departure even if the mayor returns to Parliament.
If the Prime Minister does not resign, Mr Burnham would need to secure the backing of 81 Labour MPs to mount a leadership challenge, potentially setting up a contest with Sir Keir for party members' votes.
One of Mr Burnham's supporters suggested last night that the mayor would not seek an immediate leadership fight.
Leeds MP Alex Sobel told LBC it was not his 'expectation' that Mr Burnham would immediately trigger a contest, saying he would 'come back and potentially serve in the Government, try and help us turn this Government round'.
Polling by YouGov suggested Mr Burnham would be Labour members' preferred candidate for leader, with 47 per cent saying he would be their first choice for the job.
Just 4 per cent of Labour members put Wes Streeting as their first choice, with 57 per cent saying he was wrong to resign as health secretary
Some 31 per cent ranked Sir Keir as their first choice, followed by former deputy prime minister Angela Rayner on 8 per cent.
Just 4 per cent put Wes Streeting as their first choice, with 57 per cent saying he was wrong to resign as health secretary and 15 per cent backing him in a head-to-head contest with the Prime Minister.
In a contest between Mr Burnham and Sir Keir, 59 per cent said they would back the mayor while 37 per cent would support the current PM.