Truss pledge: I would be a prime minister for the whole UK family

And she also attacked Sinn Fein for trying to “drive a wedge” between Northern Ireland and Great Britain.

The foreign secretary said that if she succeeds in becoming prime minister, she would also take on the role of 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.

Her comments were seized on by the SNP leader who said it showed Ms Truss would ignore Scotland if she wins the race for the Tory crown in a ballot among party activists.

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.

“My government would put the Union at the heart of everything it does and ensure that all corners of our country are rightly championed at the very top of government.

“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.

“I would ensure that our entire family continues to get the attention, support, and investment that it deserves.”

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.

The SNP has hit out at the comments, accusing Ms Truss of having a “total disregard” for Scotland.

Westminster deputy leader, Kirsten Oswald MP, said: “Instead of rhyming off pointless, generic rhetoric about the UK being ‘one great country’, Liz Truss must listen to the people of Scotland who voted overwhelmingly in favour of another independence referendum last year.

“The longer she denies reality, the stronger our case becomes.”

Ms Truss also hit out at the Labour administration in Wales for failing to invest in infrastructure and attacked Sinn Fein politicians for trying to “drive a wedge” between Northern Ireland and Great Britain.

In contrast, she said she would invest in infrastructure throughout the UK, such as upgrading the A75 between Gretna and Stranraer and building the M4 relief road in Wales.

She said she would also continue to work to open up new export markets for products such as Scottish whisky and smoked salmon, Welsh lamb and ships from Northern Ireland.