Liz Truss has become the 10th Conservative MP to launch a leadership bid.
The foreign secretary announced her intention to replace Boris Johnson as leader and PM late on Sunday.
Shortly after Ms Truss’ announcement, Gillingham and Rainham MP Rehman Chishti also launched his own leadership bid, tweeting: “I’m standing to be the next leader of the Conservative Party and your Prime Minister.
“For me it’s about aspirational conservatism, fresh ideas, fresh team for a fresh start taking our great country forward.”
Truss, who has served under three Tory prime ministers since being elected in 2010, has pledged to reverse the controversial national insurance hike if made leader as she insisted she can be “trusted to deliver”.
The senior Cabinet minister, who is widely expected to be a front-runner in the already crowded race, promised to “start cutting taxes from day one” to help with the cost of living.
She becomes the 10th candidate to launch their campaign, following an announcement from trade minister Penny Mordaunt earlier today.
Former minister Kemi Badenoch and senior backbencher Tom Tugendhat have also thrown their hats into the ring.
Ms Truss’ pledge to scrap the national insurance rise, which came into effect in April, mirrors that of rival Mr Javid.
It marks a departure from her defence of the policy as a minister in Boris Johnson’s Cabinet, prior to his resignation, when she was bound by collective responsibility to support the move publicly.
Ms Truss argued “it isn’t right to be putting up taxes now”, and as leader she would take “immediate action” to assist with living costs.
She said she would “keep corporation tax competitive” – hinting that she wants to look again at Mr Sunak’s plans to hike the rate in April 2023, but did not go so far as to match some of her fellow contenders’ pledges to scrap the rise entirely.
The Foreign Secretary said she would “get the private sector growing faster than the public sector, with a long-term plan to bring down the size of the state and the tax burden”.
Writing in The Telegraph, she said: “Under my leadership, I would start cutting taxes from day one to take immediate action to help people deal with the cost of living.
“I would reverse the national insurance increase that came in during April, make sure we keep corporation tax competitive so we can attract business and investment into Britain, and put the Covid debt on a longer-term footing.”
Ms Truss said her plan would get the country back on track towards becoming a “high-growth and high-productivity powerhouse”.
“It is built on a clear and longstanding Conservative philosophy, including bold supply-side reform,” she added.
The Foreign Secretary said she had “led the way” in making the most of Britain’s “new-found freedoms” outside the EU, but insisted “we can go further, whether it is doing more to champion innovation or charting our own course on regulation”.
She said she would bring “clear and decisive leadership” to Downing Street, adding: “Colleagues know I mean what I say and only make promises I can keep. I can be trusted to deliver.”
Ms Truss said the Tories can win the next election, but acknowledged it will be “an uphill battle”.
Earlier, announcing her bid for the top job, Ms Mordaunt said the UK’s leadership “needs to become a little less about the leader and a lot more about the ship”.
Candidates populated the Sunday morning broadcast round, with Mr Hunt, Mr Javid, Mr Shapps and Mr Tugendhat all making appearances to promote their campaigns.
As the race for leader heats up, more Tories have declared their allegiances.
Former Cabinet minister Michael Gove – who was dramatically sacked by Mr Johnson earlier this week – pledged his support for Ms Badenoch, while Work and Pensions Secretary Therese Coffey said she would back Ms Truss.
Andrea Leadsom, who has contended for the Tory leadership in the past, endorsed Ms Mordaunt.