Liz Truss took over as Britain's prime minister yesterday, vowing immediate action to tackle one of the most daunting set of challenges for an incoming leader in post-War history led by soaring energy bills, looming recession and industrial strife.

Truss, the fourth Conservative prime minister in six years and successor to Boris Johnson who was forced out over scandals, acknowledged the severe global headwinds from Russia's invasion of Ukraine and the Covid-19 pandemic.

"We are now facing severe global headwinds caused by Russia's appalling war in Ukraine and the aftermath of Covid. I am confident that together we can ride out the storm. We can rebuild our economy, and we can become the modern brilliant Britain that I know we can be," the 47-year-old former foreign secretary said outside her new Downing Street home and office.

Truss, who will later announce her government appointments, said she had three priorities: tax cuts to boost the economy, help over rising energy costs, and sorting out the state-run National Health Service, reports Reuters.

However, she inherits an economy in crisis, with inflation at double digits and the Bank of England warning of a lengthy recession by the end of this year.

Already, workers across the economy have gone on strike.

Truss has promised to scrap plans to increase corporation tax on big firms, and to reverse an increase in a payroll tax on workers and employers, designed to raise additional funding for health and social care, with the extra spending coming from general taxation.

"I know that we have what it takes to tackle those challenges. Of course, it won't be easy, but we can do it," Truss said, adding that Britain would also continue to stand up for freedom and democracy around the world.

One major global ally, US President Joe Biden, offered his congratulations.

Johnson, who tried to cling to power in July despite ministers resigning en masse over scandals including parties during Covid lockdowns, appealed for unity.

"It's time for politics to be over, folks," he said in his farewell speech. "It's time for us all to get behind Liz Truss."

After speaking outside Downing Street's famous black door, Johnson flew to Scotland to tender his resignation to 96-year-old Queen Elizabeth at one of her homes, before Truss followed him into Balmoral Castle to be appointed.