Centrica's British Gas, the country's biggest household energy supplier, said it would cut about 850 roles to lower costs just as official data showed unemployment hit its highest level in 15 years.

The job cuts will take place in British Gas' services business, which employs about 10,000 people, and will affect back-office management and support roles.

Earlier on Wednesday, the Office for National Statistics said jobless numbers on the International Labour Organisation measure grew by 129,000 in the three months to September to 2.622 million.

Household budgets are stretched, customers are looking for maximum value for money, and if we are going to remain competitive and offer the best prices for our customers, we need to reduce our costs, a spokesperson for British Gas said.

British Gas had raised domestic tariffs for gas by an average of 18 percent, and for electricity by an average of 16 percent in August.

Energy regulator Ofgem has said profit margins for energy firms have increased more than eight times since June as a result of rate hikes by the country's six dominant energy companies.

(Reporting by Adveith Nair; editing by Myles Neligan)