According to Ofgem, around two million energy accounts have been closed in the past five years, with many still holding credit balances.

While most dormant accounts contain only small sums, some have more than £100 waiting to be reclaimed.

Mr Lewis said consumers must take the initiative if they believe they are owed money.

He has also warned households to be cautious of unsolicited contact claiming a refund is due, stating legitimate suppliers do not typically approach former customers in this way.

Customers who switched providers within the last five years are being encouraged to check their old accounts to see whether a balance remains.

In addition to unclaimed credit, new Ofgem rules introduced this month mean customers of British Gas, Octopus Energy, EDF Energy and Ovo Energy may qualify for automatic £40 compensation payments if certain smart meter standards are not met.

| PA

Under the updated regulations, customers should automatically receive £40 in three circumstances.

These include waiting longer than six weeks for a smart meter installation appointment, experiencing a failed installation due to supplier error, or reporting a smart meter issue and not receiving a resolution plan within five working days.

Melissa Giordano, deputy director of systems and processes at Ofgem, said: “Smart meters offer customers accurate bills, cheaper tariffs, and real-time energy use tracking.

“Every customer who wants a smart meter should get one quickly, and it should work from day one.

| PA

“These new rules will set clear expectations of suppliers, drive better performance, and protect consumers when things go wrong.”

Ofgem said that since 2024 more than 900,000 faulty smart meters have been repaired or replaced following compliance action.

Customers who still have login details for a previous energy account can check for credit by signing in and reviewing their balance.

Those who no longer have access to their credentials can contact their former supplier by phone, through its website or via social media.

| GETTY

Suppliers will typically require the account holder’s name, the address associated with the account and current contact details, while providing an old account number may help speed up the process.

Consumers unsure which provider they were previously with are advised to search their email inbox for historic correspondence from energy firms.

Credit can become stranded when customers move home without updating details or cancel direct debits before a refund has been processed, leaving balances sitting unclaimed unless action is taken.