First Great Western, which made a secret agreement with the Government to run fewer carriages in order to maximise profits, has been exposed as the operator of Britain’s most over-crowded train service.

More than 270 people have to stand for at least half an hour on FGW’s 6.35am service from Bedwyn to London Paddington, despite paying more than £3,000 for their season tickets.

With 55 passengers standing for every 100 sitting, the service came top of a list of the most overcrowded trains published by the Department for Transport in response to a request under the Freedom of Information Act. FGW also operates the second most crowded train, the 6.14am from Oxford to Paddington, on which more than 160 people have to stand daily.

Last year FGW agreed a new franchise under which it agreed to pay the DfT £1.1 billion over ten years. The deal included a plan, accepted by the Government, that FGW would cut costs by removing 20 carriages from its fleet. The company was forced to bring the carriages temporarily out of storage after a fares boycott in January by commuters, some of whom had to stand in lavatories on trains that had been halved in length. But FGW plans to remove the carriages again within a year.

Four of the ten most overcrowded trains are operated by FGW. Another two are run by its sister company, First Capital Connect, which doubled some off-peak fares last year under an agreement with the DfT to pay it £800 million over nine years.

London TravelWatch, the passenger watchdog, said that the Government was largely to blame for the overcrowding and fare increases because it had signed the contracts with First in the knowledge of what it was planning to do. Brian Cooke, its chairman, said: “The Government knew the consequences of signing those deals but it was focusing on the premiums it would receive rather than worrying about the impact on passengers.”

London TravelWatch is preparing a formal complaint to the DfT about overcrowding and poor punctuality at First Great Western. A quarter of the company’s trains ran late in the year to the end of March, by far the worst record of any train operator.

In addition to commuters in Oxfordshire, FGW passengers from destinations farther afield, such as Bath, Bristol and Exeter, suffer frequent delays and cancellations.

Annual passenger growth is running at 6.3 per cent as people switch from cars to trains in order to avoid worsening congestion on roads, but the Government plans to increase the number of carriages by only 9 per cent over the next seven years. Britain’s network is now busier than at any time since 1946, with more than 1.1 billion passengers carried last year.

Mr Cooke said: “FGW is putting its passengers in an intolerable situation. Failing to stick to the timetable makes overcrowding much worse.”

The company has further angered passengers by removing most of the tables on its high speed train fleet to pack in more seats, prompting complaints from people who use laptops on board and families who can no longer sit together.

FGW said that it would reduce overcrowding on some services by running longer trains from December, but it admitted that capacity would remain a “major challenge”.

The Office of Rail Regulation said last week that the average fare rose by 6.8 per cent last year, the highest amount since the railways were privatised a decade ago.

The Government is planning to publish a 30-year strategy for the railways later this month which is expected to focus on making better use of existing lines rather than reopening moth-balled routes or building new high speed lines. However, ministers are expected finally to approve a £3.5 billion upgrade of the Thameslink route from Bedford to Brighton via London.