Martin Lewis warns thousands missing out on £3,500 a year in free money

Lewis explained how eligible retirees could cash in if their weekly income is lower than £201.95 if they are single or £306.85 if they have a partner.

The additional payment could enable thousands of Britons to receive the full State Pension of £203.85 a week.

Pension Credit could also help pensioners access additional financial benefits, including an extra cost of living payment worth £600.

The Money Saving Expert said: "Really this is something of a national tragedy because these are some of the poorest people in the country who have been paying into the system for years and they are not getting the top up to their state pension that they are entitled to.

"So this is my rough rule of thumb: If you're a single pensioner with a total income of under £220 a week, or a couple both of state pension age with total income under £320 a week then you should check - I'm not saying you will get it just that it's worth checking.

"This is worth an average of £3,500 a year."

It has been estimated that 800,000 Britons could be eligible for Pension Credit.

The figure means payments worth a total of £1.7billion remain unclaimed.

Retirees must be older than the state pension age of 65 and live in England, Scotland or Wales to qualify.

The DWP has revealed the Pension Credit programme is currently helping 1.4million retirees across Great Britain.

The Government will also launch the ‘Invitation to Claim’ mailing trial across 10 local authorities to help ensure eligible Britons get the support they need.

Eastbourne, Teignbridge, Pendle, Charnwood, Vale of White Horse, Redcar & Cleveland, Craven, Harrow, Powys and West Lothian were selected for the trial in what the Government has dubbed a “representative sample”.

Charities and broadcasters are assisting the Government in informing retirees about the programme.

Sevenoaks MP Laura Trott, who was made Pensions Minister when Rishi Sunak succeeded Liz Truss as Prime Minister, said: “We recognise the challenges some pensioners will be facing with the cost of living which is why, alongside driving down inflation, promoting Pension Credit is a priority.

“During the Week of Action, we will be out and about spreading the word – and you can help too.

“Speak to your older loved ones about Pension Credit and get them to check if they could be eligible for this vital extra support, worth an average of £3,500 per year.”