John Bercow has been quietly boosting his salary with a series of pay rises - despite Theresa May and Jeremy Corbyn turning down the extra money.

The Speaker has become the highest paid politician in Britain over recent years, with his total salary now well over £152,000 - nearly £2,000 more than the PM.

He is set to move further ahead this year as another pay rise kicks in that Mrs May and ministers have refused.

The increases have been driven by an obscure 'ratchet' in the legislation underpinning the salaries of officeholders - pushing them up in line with the average granted to senior civil servants.

They emerged as Mr Bercow faces intense pressure to be 'open' and allow an investigation into allegations of bullying staff - which he denies.

John Bercow (pictured in the Commons last week) has been facing increasing pressure to stand down as Speaker after a series of controversies and allegations about bullying of staff - which he denies

Theresa May (pictured at church with husband Philip yesterday) and ministers have declined boosts to the officeholder element of their salaries

The bumps are on top of the increases to MPs' pay, which went up by nearly 11 per cent in 2015, before rising 1.3 per cent in 2016, 1.4 per cent last year and 1.8 per cent this year - despite the rest of the public sector being restricted to 1 per cent.

Mrs May and Tory ministers have declined the boosts to the ministerial element of their salaries. Labour sources have also said the leader is respecting the freeze.

But Mr Bercow has received the extra cash, according to details slipped out by the Commons and uncovered by MailOnline. In 2015 his Speaker salary went up by 0.62 per cent, while in 2016 and last year it rose 0.42 per cent.

That meant his overall package hit £152,896 in 2017-18 - compared to £151,451 for the PM.

The increase for this year is not thought to have been calculated yet, and will be backdated to April. However, Mr Bercow is likely to benefit from a loosening of the austerity on civil service pay.

A 1 per cent rise would take his overall remuneration to £155,032, while Mrs May is now on £152,819.

A spokesman for the Speaker's Office said: 'The Speaker voluntarily took the government-wide paycut during the 2010-15 Parliament, even though he is not a member of the government, and was under no obligation to do so.

'Since 2015, his salary has been independently determined and proactively published.'

Mr Bercow has been facing increasing pressure to stand down as Speaker after a series of controversies and allegations about bullying of staff.

An inquiry led by a former judge is looking at wider cultural issues at Westminster, but will not consider specific cases. Tory MP Andrew Bridgen has asked parliament's standards watchdog to examine the claims about the Speaker - which he insists are untrue.

Tory MP Paul Scully said the 'inconsistency' of Mr Bercow's moods frustrated MPs.

He told the BBC's Westminster Hour: 'There are some days he could probably do with taking the medicament he prescribes backbenchers every other Prime Minister's Questions himself.

Jeremy Corbyn, pictured in Plymouth last week, has turned down increases to his salary as Opposition leader

Last week the Lord Speaker hinted he could approve a speech by Donald Trump (pictured) to Parliament, after MailOnline revealed the anger of peers at an extraordinary unilateral ban imposed by Mr Bercow

'I think he needs to be aware of what people are thinking and be open - these are serious allegations and I think rather than necessarily trying to close them down, be open, be upfront and say, "OK, fine, investigate and see what you find".'

Robin Fell, who served as principal doorkeeper in the Commons, said he had never experienced any bullying behaviour from the Speaker.

'My dealings with him have always been absolutely wonderful but he does have the reputation that he doesn't suffer fools gladly,' he said,

Last week the Lord Speaker hinted he could approve a speech by Donald Trump to Parliament, after MailOnline revealed the anger of peers at an extraordinary unilateral ban imposed by Mr Bercow.

Despite widespread praise for his reforms to modernise the Commons and empower backbenchers, Mr Bercow's abrasive style has infuriated many Tory MPs.

He has also faced persistent criticism of his official expenses, which have included lavish bills for chauffeur-driven cars, trips abroad and entertaining foreign dignitaries.

Mr Bercow and his family live rent-free in an opulent apartment at parliament, where the taxpayer foots a £109 a month bill for the Arsenal fan's Sky subscription.

The relative growth of the Speaker's salary partly stems from the 5 per cent pay cut David Cameron imposed on ministers as part of austerity measures in 2010.

Unlike ministers, Mr Bercow only took the reduction on the officeholder element of his pay - rather than his total remuneration package.

Ministers also offset the effects of MP pay rises between 2010 and 2015 by dropping their ministerial salaries.

Mr Bercow has kept the generous non-contributory half-salary pension traditionally granted to Speakers and PMs, despite it being forgone by every premier since Gordon Brown.

But he has said he will not claim the entitlement until he turns 65.

On becoming Speaker in 2009, Mr Bercow insisted he would only serve in the powerful role until June this year - but has since recanted and vowed to stay on.