Tory leadership favourite Boris Johnson plans to raise the level at which people pay 40% income tax from £50,000 to £80,000 at an estimated cost of £10bn.
The former foreign secretary revealed his proposal in his weekly Daily Telegraph column, with the newspaper reporting the action will cut income tax for three million people and be part-funded by cash currently reserved for a no-deal Brexit.
It will also be financed by increasing employee national insurance payments in line with the new income tax threshold.
Mr Johnson wrote: We should be cutting business taxes. We should be raising thresholds of income tax – so that we help the huge numbers that have been captured in the higher rate by fiscal drag.
We can go for much greater economic growth – and still be the cleanest, greenest society on earth.
The suggested tax cut for higher earners was immediately branded the wrong priority by Justice Secretary David Gauke, who is backing fellow cabinet minister Rory Stewart in the battle for the Conservative leadership.
Mr Johnson announced his plans on the same day two of his major challengers for 10 Downing Street formally launch their leadership campaigns.
Referring to the continuing Brexit uncertainty, Foreign Secretary Jeremy Hunt – who has picked up the much-sought endorsement of Work and Pensions Secretary Amber Rudd – will suggest the UK is facing a constitutional crisis.
And Environment Secretary Michael Gove, whose leadership bid has stalled following the revelation of his drug use, will say the stakes for Britain have never been higher.
Both men will talk about the need for a serious leader, in what may be seen as a swipe at Mr Johnson’s suitability to be prime minister.
Health Secretary Matt Hancock will also officially launch his leadership campaign on Monday and is expected to be supported by Cabinet Office minister David Lidington, who is Theresa May’s de facto deputy PM.
Vision and policies in the Conservative leadership race threatened to be overshadowed by drugs and abortion at the weekend.
Mr Gove is facing calls to withdraw from the race after admitting taking cocaine when he was a journalist.
Former Tory chairman Baroness Warsi said his continued presence as a candidate for the party leadership was completely inappropriate.
This case isn’t just about drug taking, it is about trust, she told Channel 4 News.
Mr Gove said he was fortunate not to go to prison after confessing to using the drug on several occasions.
During his launch event, he will say he can both deliver Brexit and stop Jeremy Corbyn ever getting the keys to Downing Street.
Mr Hunt, meanwhile, has been accused of attacking women’s rights after reiterating his personal view that the legal limit for abortion should be reduced from 24 weeks to 12 weeks.
The former health secretary told Sky News’ Sophy Ridge On Sunday that his own view hasn’t changed, but stressed he would not push to halve the legal limit should he become prime minister.
At his launch event, he will say Britain needs the art of tough negotiation, not the art of empty rhetoric.
He has gained the support of Ms Rudd, who said he is a winner with a track record of success in business and in government.
Health Secretary Matt Hancock will promise the country a fresh start, and former Brexit secretary Dominic Raab – also officially launching his leadership campaign on Monday – will criticise the paralysing uncertainty on Brexit.
Nominations for the Conservative Party leadership will be received by the backbench 1922 Committee between 10am and 5pm.
Candidates will require a proposer, a seconder, and the support of six other MPs to get through to the first ballot, which will be on Thursday.
Further ballots will be held on 18, 19 and 20 June.
Once the field has been reduced to two candidates, Tory party members will vote for the winner.
Those launching their campaigns on Monday are:
In what may be seen as a dig at Mr Johnson, Mr Hunt will say the country needs an experienced, serious leader at a time when Brexit remains undelivered.
At a launch event for MPs and campaigners in London, he will say: We are facing a constitutional crisis. Our new prime minister will preside over a hung parliament.
This extremely serious moment calls for an experienced, serious leader. We need the art of tough negotiation, not the art of empty rhetoric.
He will add that his background as an entrepreneur means I know there is no success without risk and as a patriot, I know there is absolutely nothing our great country cannot achieve.
Mr Gove will also use the phrase serious leader, as he too tries to move the spotlight away from Mr Johnson.
He will say: This moment right here right now is a serious time in the life of our nation. And it requires a serious leader.
The stakes have never been higher, the consequences have rarely been greater.
We need a leader who is ready to lead from day one. A leader ready to be prime minister from day one.
A leader ready to face the scrutiny of the studio lights.
Currently a 100/1 outsider to take over from Theresa May as Conservative Party leader, Mr Hancock will say the UK needs a leader not just for the next six weeks or six months, but the next six years and more.
He will say he wants his campaign to be about the future of Britain.
His mantra will be move fast and make things happen – a twist on the Silicon Valley motto of move fast and break things.
As well as discussing Brexit, Mr Raab will talk about the environment.
His plans include a national energy research centre to search for new ways to produce cheap clean energy, and a dedicated £500m international wildlife fund to boost biodiversity, species preservation, and nature conservation.
He will say: We’ve got to look to the future. We’ve got to leave the environment in a better state than we found it.