Liz Truss has received a boost in her bid to replace Boris Johnson after she received the backing of former leadership rival Penny Mordaunt.

Trade minister Ms Mordaunt narrowly lost out to Ms Truss for a place in the final two in the Conservative Party leadership race with Rishi Sunak.

Ms Mordaunt opened the latest hustings in Exeter by giving her support to Foreign Secretary Ms Truss, calling her the “hope candidate”.

The Portsmouth North MP said the Conservatives will “short-change the country, we may lose an election” if they get the decision wrong.

She said: “I could have remained undeclared, I could be off sipping pina coladas right now but I’m not because this is too important and I’m not going to leave this to chance.”

Ms Mordaunt noted choosing between the two candidates is hard, adding: “Who can lead? Who can build that team and deliver for our country? Who does have that bold economic plan that our nation needs?

“Who has got reach? Who can relate to people? Who understands that people need help with the cost of living now? And who is going to rightly clobber our opponents?

“Who is going to hold seats and win back councils and who most embodies the vision and values the British public had in their heads and their hearts when they voted in 2016 and 2019?

“At the start of this final phase of this contest, I didn’t know the answer to those questions but I’ve seen enough to know who the person I’m going to put my faith in is – and that is Liz Truss.”

Tory members cheered the announcement, with Ms Mordaunt adding: “Her graft, her authenticity, her determination, her ambition for this country, her consistency and sense of duty – she knows what she believes in, and her resolve to stand up against tyranny and fight for freedom.

“That’s what our country stands for and that’s why I know with her we can win.

“And actually seeing her over the last few weeks has made me want to help her, to help her win, to help build the team we need to win the country, and to give ourselves as a party and as a nation the pride and confidence we need to reach our full potential.

“In short folks, to give us all hope. She for me is the hope candidate.”

Ms Truss, in her opening speech, said of Ms Mordaunt: “She’s a great person, she’s a great politician, she’s a great patriot and I’m proud to call her my friend.”

The unity between the two Conservative MPs was in stark contrast to earlier exchanges in the leadership campaign, which saw allies of Ms Truss deny involvement in a “black ops” campaign against Ms Mordaunt.

The hustings event in Exeter involving Ms Truss and Mr Sunak was a calmer affair than the head-to-head television debates, with both candidates appearing separately on stage to face questions.

Ms Truss branded the Treasury a “block on progress” and hinted at making changes to the way it operates if she were to become prime minister.

Asked if the Treasury should be broken up, Ms Truss laughed as she said: “Well, I wouldn’t want to give them any advance warning if I was going to do that.”

She added: “I do think the Treasury needs to change. And it has been a block on progress.”

Former chancellor Mr Sunak criticised the Foreign Secretary’s economic plans, saying to applause: “I want to reform the corporate tax system … Liz Truss’s policies on corporate taxation are exactly the failed Treasury orthodoxy of the last 10 years, which hasn’t worked. I want to change it and grow the economy.”

Ms Truss also signalled a departure from her 2014 desire to repeal the Hunting Act 2004, a piece of legislation which led to a ban on fox hunting in England and Wales.

She said: “I remember being a minister under David Cameron’s government and looking at this issue, and I think opening Pandora’s box could possibly make the situation worse for people who enjoy country sports.”

Mr Sunak outlined a greater role for technology in reforming the NHS, explaining: “Right now we’ve got this massive problem with the backlogs and, as they’ve already done in some trusts, we can use software automation and AI to massively rip through all of the triaging and processing of them and clear up the lists, and that’s going to clear up processing times.”

But while the tone of the hustings was largely devoid of blue-on-blue attacks, Ms Truss criticised “attention seeker” Nicola Sturgeon.

She said of Scotland’s First Minister: “I think the best thing to do with Nicola Sturgeon is ignore her.”