Rail passengers are being put off from claiming compensation for the May timetable chaos because they do not believe they are eligible, a watchdog has claimed.

Transport Focus wants more Thameslink and Great Northern passengers to apply for payouts over the disruption when new schedules were introduced.

An additional industry compensation scheme worth up to the equivalent of four weeks of fares closes on January 31.

Regular travellers have "good awareness" of the scheme but some passengers are incorrectly ruling themselves out, Transport Focus found.

Its survey suggests 89 per cent of passengers who use Thameslink or Great Northern trains at least a few times a month have heard about the compensation.

But almost one in five whose journeys indicated they would be entitled to a payout did not believe they could claim, while a further 11 per cent were not aware of the scheme.

One passenger who travels from Elstree and Borehamwood to Farringdon told the watchdog: "Using an Oyster card pre-pay, I really don't know how this would work through TfL."

Another person who uses daily tickets to travel from St Albans City to London St Pancras said: "I assumed it's just for season ticket holders.

"Also, I claimed compensation for individual journeys already so don't know if I'm entitled to more."

Transport Focus has urged Govia Thameslink Railway (GTR) to do more to tell passengers they can lodge claims even if they have applied for the firm's usual Delay Repay or enhanced compensation for disruption during the qualifying period, which runs from May 20 to July 28.

The watchdog also called on the company to tell Oyster pay-as-you-go users it is acceptable to only submit their Oyster card number, as it can check journey histories using its records.

Transport Focus chief executive Anthony Smith said: "It's important that more Govia Thameslink Railway passengers claim compensation before the deadline, so they send a clear message to the rail industry. Make a claim, make sure your voice is heard. While many passengers who've already claimed say that they found the process of doing so easy, there are many more Thameslink and Great Northern passengers who are eligible.

A spokesman for Thameslink and Great Northern said the franchises have paid out more than £16 million in additional compensation to 70,000 passengers over the timetable disruption.

He went on: "We have advertised and promoted (the scheme) extensively, and made direct contact with 175,000 people. Most people Transport Focus spoke to said they found it easy to claim.

"We have already acted on the Transport Focus recommendations and urge all our Thameslink and Great Northern passengers to check if they are eligible and make a claim."