Passengers using Greater Anglia’s cross-country and rural services have been left facing crowded trains – or no services at all – after the company had to hand back some of its most modern units before their replacements were ready.

The company is currently introducing a fleet of brand-new bimode (diesel and electric) trains on rural and branch lines across the region. The Swiss-built Stadler trains are currently operating some services out of Norwich.

But only a limited number have been introduced - and now the company has had to give up some of its Turbostar units, built in the early years of the century, because they are being transferred to Wales.

And some services are now being operated by single-car trains - or have been cancelled altogether.

Mid Suffolk Green councillor Sarah Mansel who represents Elmswell and Woolpit said: "We have lost count of the number of times we have had one of these single car Class 153 units turn up on trains to Cambridge. They are full by the time we get to Bury St Edmunds and there is nowhere for the people who get on at Newmarket.

"We used to have quite good trains, but they've been sent elsewhere. The new trains are just sitting about in Norwich and Cambridge and we're having to put up with this really poor unreliable service."

She feared many people were abandoning the trains and driving instead: "Once they've stopped using the trains how will they get them back?"

There have also been problems with shortened or cancelled trains on the East Suffolk Line between Ipswich and Lowestoft.

A Greater Anglia spokeswoman said: "We apologise to those customers who have been affected by services operating with shorter trains than normal. We know how important it is to our customers that they have a seat and that our trains run on time, so our award-winning engineers do all they can to keep our trains running and delivering the planned timetable and capacity.

"We are in the process of replacing every train in our fleet with brand new trains, in a £1.4 billion investment programme, which will help further improve train performance, train reliability and service resilience, as well as providing more seat capacity.

"New trains are due to start entering passenger service on routes in Suffolk later this year, in the next stage of our roll-out, having been successfully introduced on the Norwich to Great Yarmouth, Lowestoft and Cambridge lines. We are confident they will provide a further boost to the local economy and encourage more people to travel by train rather than car.

"Our new trains must undergo a rigorous testing programme before they enter service.

"Although we try not to run one-carriage trains during busy periods, sometimes this is unavoidable, and we would rather run a train with one carriage than cancel the service altogether. However, we will always aim to run two carriage trains at peak periods.

"We have line of route technicians based around our network, who can fix some faults shortly after they have been reported so trains can go back into service quickly.

"Unfortunately, incidents such as a train hitting an animal or object can cause significant damage which means that trains are out of service due to a "fault" until repairs are completed.

"Sometimes it can take several weeks to repair a train which has been badly damaged. For example, one train which struck a herd of deer was so severely damaged it is still not back in service over two months later, despite the hard work of our engineering team.

"We have also suffered five instances of trains being damaged after striking trees blown onto the track during high winds.

"So far four diesel trains have been returned to the leasing company, whereas we now have 11 new trains in our fleet, so it is the unfortunate incidents around the network causing the challenges, not the sensibly phased transfer away of the current fleet, as they are replaced by new trains."