SCOTS living in the north of the country will be hit hardest by a Scottish Gas price hike with bills rising by as much as 4% higher than those in the south of England.

Parent company British Gas has announced it is to increase its average electricity bills by 10.4% and gas tariffs by 8.4% in the latest blow to family finances.

However, due to the costs of using the different electricity grids in the UK, customers living north of Perth will suffer an average rise of 11.2% - the biggest in the UK - while those in the south of Scotland will endure an average increase of 9.5%. The smallest rise is a 6.8% increase in the south-west of England.

Scotland's electricity ­transmission network is split between Scottish Hydro Electric, owned by SSE, in the north and ScottishPower, which holds the licence for central and southern areas.

Centrica, which owns the ­British Gas and Scottish Gas brands, said its regional price differences reflected variations in the network costs it was obliged to pay to the transmission companies around the country.

The group, which has 800,000 Scottish customers, is the second of the "big six" providers to announce price increases this month after SSE revealed more than seven million customers will be hit with an 8.2% rise from next month.

The move sees British Gas tear up a pledge made earlier this year to use an annual earnings windfall from the cold weather to keep a lid on tariffs.

The company said it "understands the frustration" of prices rising faster than incomes, but the hike means the average annual household bill will go up by £123.

Politicians were quick to condemn the hike, with Prime Minister David Cameron advising people to switch supplier.

Mr Cameron said the ­Government was doing what it could to try to keep costs down and get new suppliers into the market.

He said: "We are legislating to say these companies have to put their customers on to the lowest tariff. But there is something everyone can do, which is look to switch their electricity or gas bill from one supplier to another."

Energy Secretary Ed Davey said consumers unhappy at the company's decision should look elsewhere as many other suppliers were offering lower prices.

Mr Davey said: "I have said to British Gas customers that if they are worried they should change. There are a range of competitors and suppliers that are offering a much better deal. And those suppliers are there because of the actions of this Government.

"In 2011, there were no ­independent suppliers able to compete with British Gas or compete with SSE, who had customers above 50,000. Now we have strong independent suppliers and customers can turn to them and I urge them to do so."

Labour Leader Ed Milliband, who has promised to freeze energy prices if he wins the next General Election, said the ruse showed there was "a real urgency" for action.

He said: "Week in, week out we see higher prices from these companies causing damage to families and businesses and frankly we have got a Prime Minister who is too weak to act.

"He is standing up for the energy companies not the consumer. The reality is that they are overcharging people in a market in a market that's not working and has broken."

British Gas said it had not taken the decision to increase prices lightly, adding the Government's "social and environmental programmes" were among the reasons for the rise in the cost of energy.