A rail commuter who regularly travels into London has said smaller replacement trains are frequently causing overcrowding.

Roy Azoulay contacted the BBC after he noticed Great Western Railway (GWR) services from Oxford to London often had serious overcrowding and on some occasions meant he was forced to miss a train.

After writing to his local MP, Mr Azoulay was told the issue was partly due to an issue with the trains’ diesel engines, which GWR was addressing with supplier Hitachi.

GWR apologised to Mr Azoulay but said the issue was affecting only 2.5% of its trains, or about one train per day.

Mr Azoulay said over the past few weeks, trains that were supposed to have nine carriages were arriving at Oxford station at “half-capacity”.

“Many passengers can’t get on the train and need to wait for the next one, or have to travel in very, very crowded conditions,” he said.

“It’s not a cheap ticket. If you need to get into London before [09:00], it’s an expensive journey and not a nice-feeling one”.

After being contacted by Mr Azoulay, Oxford East MP Anneliese Dodds forwarded him a written response from government rail minister Lord Hendy.

The letter said that “reliability caused by a specific issue with diesel engines on the IntercityExpress Trains fleet” was partly a factor.

It added that GWR was working with Japanese company Hitachi on the problem, which manufactures and maintains the trains.

GWR spokesman Dan Panes said nine-carriage trains that experienced the problem were being shortened to five carriages.

“Of course it’s not good enough… [but] we’ve been able to continue running the majority of our trains,” he said.

Mr Panes added that passengers who reserved seats but were unable to get on an overcrowded train could claim compensation.