British finance minister Jeremy Hunt will announce how he will try to speed up the world's sixth-biggest economy after the shocks of Brexit, a heavy COVID-19 hit and double-digit inflation left it lagging behind its peers.

Hunt, who is due to make a budget speech to parliament after noon on Wednesday (2330 AEDT), has dismissed calls from other MPs in the ruling Conservative Party for big tax cuts now to boost their fortunes before an election expected in 2024.

Rushed into the Treasury late last year to undo former prime minister Liz Truss's unfunded tax cut plans, he says the leap in borrowing costs after her "mini-budget" made clear the limits of relying on the bond market to fund future growth.

Instead, hemmed in by his promise to lower the burden of Britain's Stg2.5 trillion ($A4.6 trillion) of debt, Hunt will seek to tackle some of the causes of Britain's long-term economic funk.

"In the autumn we took difficult decisions to deliver stability and sound money," Hunt is due to say, according to excerpts of his budget speech.

"Today, we deliver the next part of our plan: a budget for growth."

Britain is the only G7 country where output remains below its pre-pandemic size, putting pressure on Hunt and Prime Minister Rishi Sunak with the opposition Labour Party far ahead in opinion polls.

Having ruled out a major spending spree or big tax cuts, Hunt will address the acute shortage of candidates for jobs by changing childcare and welfare rules, something he says will help get hundreds of thousands of people back into work.

He is also under pressure from junior doctors, teachers and other public sector employees who, demanding higher pay, were on strike on Wednesday in one of the biggest co-ordinated walk-outs in decades.

The armed forces also say they need more money to support Ukraine in its war with Russia.

In the short term, households struggling with high inflation and tax hikes that Hunt announced in November were told they would get a three-month extension of energy bill subsidies. Hunt is also expected to extend a decade-long fuel duty freeze.

The Treasury said the budget would offer more cost of living help to businesses too.