Millions of families are facing another jump in household bills after it was reported that UK's largest energy supplier plans to hike its tariffs.

Centrica-owned British Gas, which serves about 12 million homes, is preparing to announce as early as Friday that it is increasing electricity and gas charges in the high single percentage digits, the London Evening Standard said.

The average British Gas annual dual-fuel bill for gas and electricity currently stands at £1,260 - meaning a 5% increase would add £63, while an 8% rise would put on £100.

A British Gas spokesman said: "We do not comment on future pricing movements. We do not comment on speculation about future pricing movements."

The report comes as rival SSE prepares to increase tariffs by 9% on average on Monday, hitting about five million electricity customers and 3.4 million gas customers.

British Gas put gas and electricity tariffs up by 18% and 16% respectively in August 2011, blaming higher wholesale costs, but this was followed by a drop of 5% in electricity tariffs in January when prices eased.

The Press Association, photo by Boilers