The two prime ministerial hopefuls have each pledged new commitments if elected – with Liz Truss saying she would take on the role of ‘minister for the Union’ and Rishi Sunak promising to make Britain more “energy secure”.

Ms Truss made a promise to uphold the United Kingdom as she hit out at politicians in the devolved administrations for playing “political games” rather than delivering for voters.

The Foreign Secretary confirmed if she succeeds in becoming prime minister, she would also be minister for the Union – a position created and held by Boris Johnson.

Her intervention came after she sparked controversy by denouncing Scotland’s First Minister Nicola Sturgeon as an “attention seeker” suggesting she would ignore her demands for a fresh referendum on independence.

Meanwhile, Mr Sunak has committed to introducing legislation to make the UK “energy independent” by 2045 at the latest, as he vowed to ensure there is no repeat of the looming winter crisis.

The former chancellor said if he took on the role at Number 10 on 5 September, he would put in place immediate support for households – particularly the most vulnerable – faced with soaring energy bills, as well as boosting North Sea gas production.

He would do this, he said, by deregulation which would allow gas production to increase over the winter.

Regulations governing offshore wind, rooftop solar and nuclear would be overhauled to scale up supply, while fracking for shale gas would be allowed where there is local consent, he added.

‘We are not four separate nations’

In a statement, Ms Truss – who remains the clear favourite to succeed Mr Johnson – insisted she would govern for the whole UK “family” if she gains the keys to No 10.

“Having grown up in Paisley before going to a comprehensive school in Leeds, I consider myself a child of the Union. When I say I will deliver for our country, I mean all of it,” she said.

“For too long, people in parts of our United Kingdom have been let down by their devolved administrations playing political games instead of focusing on their priorities. If elected prime minister, I will deliver for our whole country.

“We are not four separate nations in an agreement of convenience, as some would have us believe. We are one great country which shares a history and institutions, but also family and friends, memories and values.”

Read more:
What have Truss and Sunak pledged for the country so far?

Ahead of a visit next week to Scotland, she accused the SNP of being preoccupied with the issue of independence when, she said, they should be focused on averting a recession.

However, the SNP hit back, saying she had “a total disregard for Scotland”.

Mr Sunk concentrated his efforts on the energy crisis, also pledging the creation of a new energy security task force and

He said he would take steps to radically reduce energy waste, with low cost measures to insulate millions of homes.

In the longer term, he promised to reform the energy market – which was no longer “fit for purpose” – to cut bills, with the establishment of a new dedicated energy department to lead the change.

Labour, meanwhile, was not impressed.

Ed Miliband, shadow climate change and net zero secretary, said he didn’t believe “the man who dragged his feet for months on the windfall tax, then introduced a massive loophole for oil and gas companies” could “tackle the bills crisis the British people face”.

He added: “The truth is, that both Rishi Sunak and Liz Truss just don’t get it when it comes to the scale of the emergency families are facing.”