Andy Burnham could be poised to be the first prime minister to enter Downing Street with an openly Catholic faith - nearly 500 years after Henry VIII split from Rome.

The Greater Manchester mayor is currently contesting the Makerfield by-election with a view to returning to Westminster to oust Keir Starmer from office.

If he is successful in his bid to replace Sir Keir as PM, the 56-year-old's entry into No10 would raise some constitutional challenges.

Under a law from the 19th century, Mr Burnham - as a Catholic - would be barred from advising the King on top appointments to the Church of England.

The Roman Catholic Relief Act of 1829 states that anyone breaking this law shall be 'deemed guilty of a high misdemeanor, and disabled for ever from holding any office'.

But, in practice, Mr Burnham would simply be able to hurdle those challenges by delegating the duties - which are largely a formality - to another government minister.

It is a constitutional conundrum that was previously raised when Boris Johnson was prime minister.

Mr Johnson is widely accepted to have been Britain's first Catholic premier, despite him having technically entered Downing Street in 2019 as an Anglican.

When he was a baby, Mr Johnson was baptised into his mother's Catholic faith. But he was later confirmed into the Church of England while a pupil at Eton College.

The Tory politician was then said to have 'reverted' to Catholicism when he married Carrie Symonds at Westminster Cathedral - the largest Catholic church in England and Wales - while he was PM in 2021.

But Mr Johnson rarely discussed his faith in public during his time in No10. When asked by ITV News if he was a practising Catholic following his marriage to Carrie, he replied: 'I don't discuss these deep issues.'

It was reported at the time of his wedding that Mr Johnson would pass his duties on Church of England appointments to his Lord Chancellor, Robert Buckland. 

Tony Blair similarly did not talk about religion when he was Labour PM between 1997 and 2007.

'We don't do God,' former Downing Street spin doctor Alastair Campbell is famously reported to have said when his boss was asked about his faith. 

But, shortly after leaving No10, Sir Tony converted to Catholicism - a decision he said had been driven by his wife, Cherie.

'Ever since I began preparations to become a Catholic, I felt I was coming home... this is now where my heart is, where I know I belong,' the ex-PM told a Communion and Liberation meeting in 2009. 

He added: 'Frankly, this all began with my wife. I began to go to mass and we went together. We could have gone to the Anglican or Catholic church – guess who won?'

When Gordon Brown, a Presbyterian, succeeded Sir Tony as PM, he watered down his office's role in the appointment of Church of England bishops.

Mr Burnham has been open about his Catholic faith in the past, telling the Guardian in 2009 that the three most important things in his life, aside from family, are 'Everton FC, the Labour Party and the Catholic church - in that order'.

The Greater Manchester mayor, who was born in Merseyside, inherited his Catholic faith from his mother and attended Catholic schools during his childhood.

He has spoken about how his non-Catholic father was worried about meeting his mother's family for the first time 'as religion was so important in Liverpool then'.

But the strength of his faith appeared to have fluctuated in 2015, when he told the Huffington Post website: 'I'm Catholic by upbringing, but I'm not particularly religious now.'

The father-of-three added: 'My kids go to a Catholic school, so I still believe in the values and the grounding it gives you, I'm a very big believer in that.'

In the same interview, Mr Burnham suggested the Catholic Church had lost touch with millions of ordinary British Catholics on issues like gay rights and birth control.

'I find that quite difficult because if I think of the church of my youth, and the priests that I knew, the feeling and overriding mood was quite forgiving really, quite humane, humorous, irreverent, even the priests,' he said.

'That's my memory of the church that I grew up with. And it seemed at some point... to click into a more judgemental mode and became much more obsessed with sexuality and issues related to sexual behaviour.'

But Mr Burnham stressed he still values his Catholic upbringing, adding: 'Catholic social teaching underpins my politics.'

Last year, the Government suggested it was unlikely it would make any changes to the Roman Catholic Relief Act of 1829 or the Jews’ Relief Act of 1858, which prohibits anyone of Jewish faith from advising the King on Church of England appointments.

In reply to a written parliamentary question, Cabinet minister Nick Thomas-Symonds said: 'The Government recognises that there are historical restrictions in statute on Roman Catholic and Jewish people making and advising the Crown on Church appointments.

'The Government will keep this matter under review but, given other pressing issues, this is not a current priority.'