British Gas, the UK’s largest energy supplier, is to announce an increase in its electricity and gas prices in a move that could push more hard-pressed consumers into fuel poverty.

British Gas, which is owned by Centrica and serves some 12m homes and nearly 1m businesses, will on Friday announce it is to raise tariffs by 7-8 per cent, a person familiar with the matter said. The price rises are expected to come into effect in mid November.