A WATCHDOG is under attack for doing too little to help thousands of people on low incomes who are "trapped" in costly deals with their energy supplier.

Glasgow MP John Robertson said Ofgem had to "get a grip" and that their "inertia" was affecting people's lives.

He called on the Government to reform the organisation, which regulates the utilities market, after the Coalition pledged to meet Ofgem to discuss the issue of "debt blocking".

Campaigners warn that hundreds of thousands of customers on modest incomes are stuck with their energy company because they are prevented from switching suppliers if they owe more than £200.

Critics say the process is keeping customers on unaffordable tariffs.

Figures compiled by the House of Commons library suggest that raising the limit to £350 would allow 200,000 people to change energy suppliers.

The limit applies to pre-paid meters, used by an estimated one in 10 customers, many on low incomes.

They allow customers to pay in advance, so they are not caught unable to pay their bill. But these consumers cannot shop around for the best deal, as ministers recommend.

In 2009 Ofgem found millions of customers using pre-payment meters were being overcharged.

The regulator set the £200 limit in 2006, but campaigners claim it is too low and has not risen with inflation.

Mr Robertson, who sits on the Energy and Climate Change Select Committee, said: "We are trapping some of the poorest families into fuel poverty, and weighing them down under an insurmountable debt mountain.

"It is not fair and shouldn't be happening when energy companies are filling their boots, raising prices at the customer's expense," he added. "Ofgem need to get a grip, as they take too long to respond to changes in the energy market, and their inertia is affecting the lives of thousands of poor customers."

Soaring energy bills have pushed the cost of running a home to the highest level in a decade, research showed at the weekend, with rising utility prices accounting for 92% of the rise in the past year.

Last year, ministers blamed rising energy costs after one- third of Scottish households were found to be in fuel poverty, calculated as when energy costs eat up more than 10% of income. The figure had more than doubled since 2002.

The statistics, which were taken from the Scottish House Condition Survey, also showed the number of households in "extreme fuel poverty" had risen from 3% in 2002 to 10% in 2009.

Last month, a report commissioned by the UK Government warned that fuel poverty was also likely to worsen in coming years.

The problem has been linked to almost 4000 deaths a year across the UK.

A spokesman for Ofgem said: "As part of our retail market review we are looking at whether there are any barriers to switching that need to be removed."