Heating oil customers whose orders were cancelled during a sharp price rise are set to receive compensation of up to £350 following an investigation by the Competition and Markets Authority (CMA).

The watchdog says about 1,700 customers were affected by possible breaches of contract. They received refunds, but some then faced higher prices for replacement oil or went without. At its April peak, heating oil rose 92% to 123p a litre amid the Iran war.

Several suppliers have agreed to make amends after the CMA contacted them. Customers who paid more for replacement oil will receive the difference; those who did not buy more will have their original orders honoured at the agreed price. The regulator is still seeking compensation from other suppliers and says it may take court-based enforcement action.

About 1.5 million UK households, mainly in rural areas without mains gas, rely on heating oil. The CMA found that the wider price rises largely reflected wholesale costs, but has recommended new rules for suppliers, including standards for handling cancelled orders.