Britain pledged today to cap wholesale electricity and gas costs for businesses at less than half the market rate from next month.

The move will help relieve the pressure of soaring energy costs but will add to the UK government's fast-rising spending.

Wholesale prices for electricity will be capped at about £211 per megawatt hour (MWh) and for gas at £75 per MWh, compared to forecast market rates of £600 and £180 respectively.

"We have stepped in to stop businesses collapsing, protect jobs and limit inflation," finance minister Kwasi Kwarteng said.

Wholesale gas and electricity prices in Europe surged after Russia invaded Ukraine and have remained volatile since.

Groups representing businesses from pubs to steelmakers welcomed the intervention, saying the government had thrown a lifeline to companies battling to survive.

The government did not publish any estimate of the cost, but reports have put the price of six months of support at up to £42 billion, on top of more than £100 billion for a previously announced scheme to help households.

The final unit prices will be confirmed on September 30.

Suppliers will be compensated for the reduction in wholesale gas and electricity unit prices that they are passing onto non-domestic customers, the government said.

After weeks of political stasis while the governing Conservative Party elected a new leader and the country mourned the death of Queen Elizabeth, Kwarteng is due to give a fiscal statement on Friday.

This is expected to set out some detail on how he will pay for the energy scheme while at the same time delivering on promises to cut taxes, although the total cost of the energy scheme will depend on market prices over the coming months.

Investors say Friday's statement will be a critical test of confidence in British public finances as borrowing costs rise at the same time as a commitment to higher spending and banking on accelerated economic growth to pay for it.

Kwarteng said today he had pledged to get debt down in the medium term, but it was "absolutely right" to help families and businesses in the face of a major economic shock.

The business energy scheme will initially apply from October 1 to March 31, 2023, for all non-domestic energy users, including charities and the public sector such as schools and hospitals as well as businesses.

The UK government also today announced support for households in Northern Ireland on the same level as the equivalent scheme in the rest of the United Kingdom.