Energy firms could face much stricter long-term restrictions on their use of prepayment meters as regulators announced a review of their rules following a Times investigation.

Ofgem, the energy regulator, wrote to suppliers on Wednesday, stating that it was beginning an “intensive consultation process” into the use of prepayment meters and whether “rules and guidance should be amended going forward”.

The review is due to take six weeks and will include evidence from energy suppliers, consumer groups and charities.

Ofgem will also invite individuals to submit evidence about their treatment by energy firms. It will announce a separate route for this next week.

The action comes after an undercover Times reporter found that British Gas was routinely sending debt collectors to break into customers’ homes and force-fit prepayment meters, even when they were known to be extremely vulnerable.

If families cannot afford to top up these pay-as-you-go meters, their heating or electricity is cut off.

• Exposed: How British Gas debt agents break into homes of vulnerable

Families forced on to the meters last month included a single father with three children. Others targeted despite freezing temperatures and rocketing energy prices included the mother of a four-week-old baby and a woman in her fifties known to have severe mental health problems.

The debt collection agents were given the incentive of bonuses when they force-fit prepayment meters.

Following publication of the Times investigation, Ofgem asked all suppliers to stop force-fitting prepayment meters. The suspension will last at least until the end of March, allowing for time to consider longer term changes to protect vulnerable customers.

Ofgem also issued a legal order banning British Gas from force-fitting the meters until it can prove it is complying with all its legal obligations.

Lord Justice Edis, one of the country’s most senior judges, has ordered courts to stop listing hearings to authorise warrants for energy companies to force-fit the meters in customers’ homes “until further notice”.

Centrica, which owns British Gas, apologised for its agents’ conduct and suspended the practice following an approach by The Times before publication of the findings.

Last year there was a surge in the number of applications to courts for warrants to force entry into customers’ homes and fit a prepayment meter.

Under Ofgem rules, forcing customers onto prepayment meters under warrant should only ever be a last resort, and should never occur when customers are “in very vulnerable situations”.

The regulator guidance suggests vulnerability could include being of state pension age, having a disability, a mental health condition, being pregnant, or having children under five years old.

In its letter to suppliers yesterday, Ofgem’s chief executive, Jonathan Brearley, said its review would “consider how the rules and guidance on the use of prepayment meters by suppliers apply in the current exceptional circumstances as well as whether these rules and guidance should be amended going forward”.

Brearley also indicated that all households may have to pay more in future to enable suppliers to recoup their costs if the suspension on forced prepayment meter installations leads to an increase in unpaid bills.

He stated that this was a “difficult balance”, adding: “If this debt cannot be recovered from some customers, then this increases costs for suppliers.”

Ofgem sets the energy price cap based on its assessment of the costs suppliers face and already includes an allowance for recovering “bad debt” or unpaid bills that are not expected to be recovered. Ofgem told suppliers that “if an adjustment is required, we will act quickly”.

At present, consumers are shielded from paying the full amount they would be charged under the price cap thanks to the government’s energy price guarantee, which subsidises tariffs so that a typical household won’t pay more than £2,500 a year. This is due to rise to £3,000 a year in April. In the second half of the year the energy price cap is forecast to fall below this level, meaning it will set the ceiling on bills once more.

Grant Shapps, the energy secretary, also wrote to energy suppliers in light of the Times investigation, asking them to urgently set out plans to identify customers who may have had prepayment meters wrongfully installed and to compensate them.

Last week, he said he was disappointed at the responses from the firms, many of whom had “failed to address” the issues he had raised.

“I am angered by the fact some have so freely moved vulnerable customers on to prepayment meters without a proper plan to take remedial action where there has been a breach of the rules,” he said.

Centrica said it had only used warrants as a last resort after several attempts to resolve issues with customers. It recently announced a £10 million fund for prepayment customers. A spokeswoman said: “Protecting vulnerable customers is an absolute priority.”