LONDON - Liz Truss has promised to announce a plan to deal with soaring energy costs within a week if she becomes prime minister.

The Tory leadership hopeful, the favourite according to pollsters, told the BBC’s Laura Kuenssberg she would “act immediately” to help with bills.

But she offered no details, saying she would need time in office first in order to finalise exact proposals. Her rival Rishi Sunak said he would target further payments at the poorest.

One of the two contenders will be announced as the next Tory leader on Monday, and will replace Boris Johnson in Downing Street the next day.

They have come under pressure to spell out how they would protect households with rising bills, as well as give help to businesses, which are not covered by the domestic price cap.

Speaking on BBC One’s Sunday with Laura Kuenssberg, Foreign Secretary Ms Truss said action on energy bills would be “vital” for people and the economy. She added that further support would need to go “hand in hand” with a plan to boost domestic energy supplies, arguing the UK had become too dependent on international energy prices. Mr Sunak said further energy payments to pensioners and the low-paid, beyond those he announced as chancellor, should be targeted at pensioners and the low-paid. He has argued his suggested cut to VAT on energy bills would also provide some help for all. He also said he couldn’t rule out the prospect of blackouts over the winter to ration supplies, as the situation was “serious” and “every tool in the toolbox” would be needed.

“Of course we don’t want to be in that situation, but I think it’s responsible not to rule it out,” he added. Ms Truss has promised to deliver around £30bn in tax cuts in an emergency Budget later this month if she wins, including a reversal of April’s rise to National Insurance. Pressed on whether richer people would benefit more from the cut, she said: “The people at the top of the income distribution pay more tax - so inevitably, when you cut taxes you tend to benefit people who are more likely to pay tax.”