The state of the social care system in England is a topic that’s made Andy Burnham angry for decades.

As Gordon Brown’s health secretary he proposed a compulsory levy collected from people’s estates – an idea the Conservatives dubbed the “death tax”.

He repeatedly returned to the issue when making interventions as the Mayor of Greater Manchester, and in his first major interview as prime minister back in July, Burnham pledged to put “whatever political capital I have into fixing broken social care”.

We now have the first outline about how he hopes to do that.

But there are a host of unanswered questions about how the government would fund and deliver what could be an eye-wateringly expensive and politically perilous idea.

The prime minister told the BBC’s Sunday with Laura Kuenssberg that he will go into the next election proposing a free-to-use, universally funded national care system.

Past governments have looked at how to reform social care and balked at the potential costs.

The Health Foundation has previously estimated that a free system could end up costing the taxpayer around £18bn a year.

Burnham denied that figure but conceded that tackling the issue could make him “unpopular” with some.

He stressed that the current system comes with hidden costs for individuals and the state, such as people losing their houses to pay for costs and spending time in A&E because their home care isn’t adequate.

But it’s difficult to deny that this idea would come with a staggering up front cost and one the prime minister would have to lay out a far more detailed funding plan for, if he went into an election with this as his flagship proposal.

The last prime minister to attempt a substantial overhaul of social care was Theresa May, whose 2017 plans unfurled when they were nicknamed the “dementia tax”.

Burnham said the manifesto that Labour was elected on at the last general election would make it “hard” to achieve his goal.

That’s a clear hint that he could well go into the next election pledging to increase tax in order to fund social care.

The manifesto that Burnham is currently bound by pledged not to hike income tax, VAT or National Insurance.

Other funding options are not being taken off the table, including a return to Burnham’s old plan to make some people pay out of their inheritance.

He could also get some political cover, in the form of an ongoing review by the longtime policy guru Baroness Casey.

She’s been heading a commission into adult social care since April last year and Burnham said her findings would influence what he proposes.

It’s understood she’s been asked to find a “sustainable” solution, and it would be within her remit to recommend tax changes and cuts to other areas of spending, to raise the money needed.

The prime minister wouldn’t engage with the question of what areas he might cut but did promise more meat on the bones of his social care plans when he makes his speech to the Labour Party conference on Tuesday.

Darren Jones, who was Sir Keir Starmer’s chief secretary, and has assumed the mantle of an internal Burnham critic, warned against taxing, spending and borrowing, without making cuts.

He suggested that if Burnham wanted to prioritise social care, he may need to look at scrapping the triple lock for pensioners, which Labour’s 2024 manifesto pledged to keep.

The Conservatives have already criticised the potential for increasing the tax burden and Reform have described Burnham’s plan as another “death tax”.

Some Labour MPs would undoubtedly be uncomfortable at the prospect of having to sell controversial decisions like tax rises or changes to the triple lock, on the doorstep at the next election.

But there’s been a general trend in recent years among both the Conservative and Labour parties, of backbenchers grumbling about party leaders being unwilling – perhaps not brave enough – to make forthright political arguments.

Burnham hasn’t yet revealed the finer details, but for now, at least, he’s confident enough in his own ability to win the argument.

Those around the PM believe there are enormous plaudits to be won for whoever manages to adequately fix the system.

History would suggest, though, that prime ministers who fail to convince the public on social care reforms don’t last long in the job.

It may be an issue he’s talked about for years, but on social care, Andy Burnham is taking a big swing.

Sign up for our Politics Essential newsletter to keep up with the inner workings of Westminster and beyond.