Rail freight operators have stopped using electric trains and switched to diesel locomotives due to soaring energy prices.
Firms cannot absorb the three-fold increase in the cost of electricity, according to trade body Rail Freight Group (RFG).
The decision to mothball electric freight trains, which result in lower CO2 emissions than diesel models, was made less than three weeks before the Cop26 climate conference in Glasgow.
RFC said in a statement: “The current significant increase in the wholesale cost of electricity for haulage means that some operators have had to take the regrettable decision to temporarily move back to diesel locomotives.
“A 200% increase in electricity costs for each train cannot be absorbed by the operators, or customers, and so necessary action is being taken to ensure that trains can continue to operate delivering vital goods across the country.
“Our members are assuring us that this is a temporary measure and will be kept under constant review.”
The statement added that road freight emits 76% less CO2 than road freight “even with use of diesel locomotives”.
A spokesman for freight operator Direct Rail Services said: “Our fleet of locomotives offers the flexibility to adapt to changing market conditions while maintaining a safe, secure and reliable service.
“That might mean we change the type of traction we use on our train services in response to temporary fluctuations in energy prices.”
He added that the firm is “committed to low-carbon rail freight”.
Another operator, GB Railfreight, told magazine International Railway Journal it had taken the “difficult decision” to replace their electric services with diesel locomotives “in order to maintain a cost-effective solution for transporting essential goods and supplies around the UK”.
Industry body the Rail Delivery Group said some train operators “may need to take short-term action to afford their bills”, but many firms join forces to buy electricity in bulk to protect themselves from sudden price rises.
The maximum price of approximately 80% of the total electricity used to power trains in Britain is fixed until around April 2024.
A Network Rail spokesman said: “Electricity costs for Network Rail and passenger operators were negotiated some time ago and are fixed for this year and most of next.
“A few operators, however, are subject to the current market wholesale price of electricity that Network Rail passes on directly at cost.
“Despite this, rail remains the most carbon efficient means of moving large quantities of both freight and people around the country.”
Office of Rail and Road figures show 422 kilotonnes of CO2 equivalent emissions were made by diesel locomotives in the year to March 2021.