Work and Pensions Secretary Amber Rudd has backed Jeremy Hunt for the leadership of the Conservative Party as the Tory leadership campaign formally starts.
Her support for the foreign secretary will be a blow to Micheal Gove, another leadership candidate, in the battle to attract Tory moderates to their bid.
The MP also appeared to take a swipe at Boris Johnson when remarking it was time to reject “more bluster”.
She said: “These are serious times and we need a respected statesman who Brussels will listen to, not more bluster.
“Jeremy is a winner with a track record of success in business and in government.”
Meanwhile, Hunt will say the country needs a leader who offers more than “empty rhetoric”.
Hunt will say an “experienced, serious leader” is needed to deal with the constitutional crisis caused by Brexit.
The Foreign Secretary will launch his campaign with endorsements from the worlds of sport and health – his two previous cabinet roles.
At an 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.”
Hunt will say 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”.
Johnson himself is drawing up plans to raise the 40p income tax threshold to £80,000 at a cost of almost £10 billion.
The higher rate of income tax currently applies on earnings over £50,000 in England and the move could benefit more than three million people.
The former foreign secretary believes the cost of the policy could be met through some of the cash set aside for no-deal Brexit planning.
In his regular Daily Telegraph column, he said: “We should be cutting corporation tax and other 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.”
Elsewhere, Matt Hancock is promising to offer the “fresh start” the country needs as the Health Secretary launches his campaign to become the next Prime Minister.
Speaking on Monday, he will argue the country needs “a leader not just for the next six weeks or six months, but the next six years and more”, and will set out his vision to make the next decade “the soaring twenties”.
Currently a 100/1 outsider to take over from May as Tory leader, he will say he wants his campaign “to be about the future of Britain”, adding that “inside the heart of every person there is something of value”, with the role of Government to “help them release it”.