Liz Truss has said her loyalty to Boris Johnson prevented her from quitting along with dozens of colleagues last week, as she pledged she is the candidate that can "deliver". 

After placing third in the first ballot of Tory MPs, the Foreign Secretary presented herself as the most experienced contender as she stressed her competency surrounding Brexit and defence. 

“We are at a critical moment for our country," she said opening the speech.

“Now is the time to be bold, we cannot have business-as-usual economic management, which has led to low growth for decades," she added in an apparent swipe at competitor Rishi Sunak. 

She pledged she would be ready to be prime minister from "day one" as she officially launched her campaign for the top job with a speech in central London.

Speaking on her relationship with Boris Johnson, Ms Truss said she was "loyal person" and remains "loyal" to him despite a series of scandals triggering mass resignation of senior ministers and parliamentary private secretaries. 

“I am a loyal person. I am loyal to Boris Johnson. I supported our Prime Minister’s aspirations and I want to deliver the promise of the 2019 manifesto.

“What we need to do now is deliver, deliver, deliver, and I am the person in this race with the record of delivery.”

Despite admitting she did not have a conventional Tory background, Ms Truss promised to deliver Conservative values while in office.

She said: "I will campaign as a Conservative and I will govern as a Conservative.

“I am ready to be prime minister from day one.”

However, while she promised to continue the Government’s levelling-up ambitions, she also pledge a change of tack on the economy and to reverse the planned rise in national insurance.

She also told the launch that she wants to see defence spending rise to 3% of GDP by the end of the decade as well as stressing that she agrees “completely” with the Government’s controversial Rwanda asylum policy.

Ms Truss dodged questions about worries she could be outflanked by rival Penny Mordaunt, instead stressing the wide array of talent the leadership contest is displaying.

A recent YouGov poll of Conservative party membership revealed Ms Mordaunt would beat Ms Truss in a head-to-head battle by 55% to 37%. 

Ms Truss' campaign launch came after former Brexit minister Lord Frost launched a scathing attack on Ms Mordaunt, saying as his deputy she had lacked a grasp of the detail and was unwilling to deliver tough messages to Brussels.

Asked about those accusations, Ms Truss said she would not be making any “disparaging comments” about her rival.

“The Conservative race shows what a broad range of talents we have in the Conservative Party. And we didn’t get there through identity politics,” she said.

“We didn’t get there through quotas. We got there because we are a meritocratic party that believes in the future of Britain.”

Former Tory leader Iain Duncan Smith, Culture Secretary Nadine Dorries and Work and Pensions Secretary Therese Coffey were among the high-profile names in the audience, while Business and Energy Secretary Kwasi Kwarteng introduced Ms Truss.

The Foreign Secretary said: “What the British people are crying out for is a modern and united Conservative Party, ready with the courage of its convictions to deliver on the promises that we have made.”