Andy Burnham has claimed his devolution plans strengthen his case for a written constitution for the UK.
The prime minister said the UK’s “antiquated” political system needs reform if equal opportunities are to be effectively shared out across the country.
Britain is one of the only major democracies without a codified arrangement which lays out how the country should be governed.
The UK’s constitution is currently established through history by common law, statutes and conventions.
Burnham has already decided to allow regional mayors to keep a proportion of income tax to spend on their local area by early 2028.
He has also set up No.10 North, an alternative to 10 Downing Street in the north of England, to symbolise his commitment to moving power out of Westminster.
He said his devolution plans “increase the case for a constitution because Britain is changing through this, England is certainly changing through this.”
He claimed the country needs to set up a codified model of devolution which works for Wales, Scotland, Northern Ireland and England.
“In the end, I think it does start to point towards a new constitutional settlement… with that commitment to equivalent living standards,” he said.
He added that his promise to implement “good growth in every postcode” was “more than just a sound bite”.
The prime minister did not outline any time frame for implementing such a historic change.
Countries usually adopt a written constitution following major events like revolution or war, when governments need to signal a departure from previous regimes.
The prime minister first floated the idea in his 2024 book Head North, co-written with Liverpool city region mayor Steve Rotherham.
He said deep inequality had become part of Britain because it had not moved on from the “feudal state” which held power in Westminster.
“Our failure fully to set out the rules for how the country should be run is one of the principal reasons why Britain is one of the most unequal major countries in the world,” he wrote.
“Our unwritten and murky constitutional arrangements have had the effect of hoarding power in a small number of hands – in Whitehall and Westminster and, by extension, in the powerful networks of institutions and vested interests that surround them.”.