Liz Truss has promised to deal with surging energy costs and to cut taxes, after she won the Tory leadership contest to become the next PM.
Her plan, set to be announced on Thursday, is likely to include a freeze on energy bills - though precisely how it would work is still unclear.
Ms Truss will be formally appointed by the Queen at Balmoral Castle later, after a final speech by Boris Johnson. The 47-year-old, the UK's third woman PM, will then appoint her cabinet.
In her victory speech, Ms Truss promised a "bold" programme of tax cuts to grow the flagging economy and to prevent the UK tipping into recession.
She will officially take the reins of power on Tuesday, bringing Mr Johnson's turbulent premiership to an end less than three years after the Conservatives' resounding election victory in 2019.
Ms Truss's most pressing decision as premier will be how best to shield households and businesses from the soaring international price of energy.
On Monday, Ms Truss told party activists at London's Queen Elizabeth II conference centre she would "deliver on the energy crisis" by dealing with bills and boosting the UK's domestic energy sources.
Under her plans, it is understood energy firms would be able to take out government-backed loans, which they would use to freeze or lower customers' bills. The loans would be repaid from bills over the next 10-20 years. Scottish Power, which proposed government-backed loans, has estimated that freezing bills for two years could cost nearly £100bn.
Small business are also expected to be offered some energy bill relief, though the details may not be included in Thursday's announcement.
Ms Truss beat rival Rishi Sunak with 57% of the vote, a narrower win than expected. Those predicted to join her top team include Kwasi Kwarteng as chancellor, former leadership rival Suella Braverman as home secretary and James Cleverly as foreign secretary.
Home Secretary Priti Patel and Culture Secretary Nadine Dorries said they would step down as senior ministers once Ms Truss becomes prime minister.
Mr Johnson congratulated Ms Truss on her victory and said she had the right plan to "unite our party".
Ms Truss paid tribute to her "friend" Mr Johnson in her victory speech, adding he would be "admired from Kyiv to Carlisle" for his record in office.
"Boris, you got Brexit done, you crushed Jeremy Corbyn, you rolled out the vaccine and you stood up to Vladimir Putin," she said.
In a break with tradition, the outgoing and incoming prime ministers are expected to travel to Balmoral Castle in Scotland for the handover of power, rather than Buckingham Palace.
The Queen has been suffering from mobility issues and it is understood the change was made to prevent the need for any last-minute rearrangements.
Ms Truss has promised £30bn in tax cuts in an emergency Budget later this month, having blamed the tax burden for the UK's sluggish growth.
Her proposed cuts include reversing the rise in National Insurance under Mr Johnson's tenure, temporarily ditching green levies on energy bills, and scrapping a planned rise to corporation tax.
As well as the domestic agenda, her in-tray also includes continuing to support Ukraine after its invasion by Russia and repairing a fractious relationship with the EU over Northern Ireland.
Former chancellor Rishi Sunak, who attacked her economic plans during the campaign, told the BBC he would offer her his "full support".
He said he will stand again to be an MP at the next general election, but is not expected to be in Ms Truss's cabinet.
Labour has called on Ms Truss to expand the windfall tax on the profits of oil and gas companies to part-fund a six month freeze to domestic prices.
The party followed the Liberal Democrats earlier this summer in backing a freeze, along with the SNP.
Ms Truss, however, has ruled out further windfall taxes, saying during the campaign it "sends the wrong message to international investors".
Speaking earlier, Labour leader Sir Keir Starmer pledged to work with Ms Truss to deliver a freeze, saying there was cross-party agreement on the idea.
He criticised her approach on the economy, arguing she had talked more in her campaign about cutting taxes for businesses than the cost of living crisis.
"That shows that not only is she out of touch, but that she's not on the side of working people," he added.
Lib Dem leader Sir Ed Davey told BBC Breakfast Ms Truss's reported plan was not a freeze on energy bills but a loan and said instead energy companies should pay via a one-off tax on profits.
"What they are saying is families and pensioners should be paying for this for years to come," he said.
SNP leader and Scottish first minister Nicola Sturgeon called for the price freeze to include businesses, which are not normally covered by the UK's energy price cap, and extra cash support.
Source: BBC
Image source: Reuters
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