Serious concerns about the reliability of East Anglia's ageing commuter trains were heightened last night after a breakdown caused hours of delays on the Norwich-London mainline.

Passengers had to add an extra two hours to their journey times yesterday after a National Express East Anglia service lost power near Diss.

The breakdown has raised another question mark about the rail network's ability to cope – not least with the demands of ferrying thousands of sports fans to the Olympic Games in London next year.

The delays came after the government pushed back the start date of a long-term rail franchise for Greater Anglia by 12 months, which means that passengers are unlikely to see any major investment in services until 2014.

Campaigners said the latest delays highlighted the need for new rolling stock on the Norwich-London line, which is more than 30 years old.

A new train operator is set to take over a short-term franchise from National Express East Anglia (NXEA) in February. But the three companies bidding for the contract – Abellio Greater Anglia, Eastern Railway and Stagecoach Anglia Trains – have been told by the government that the successful new operator will run services for 29 months and not 17 months as first planned. The extension until July 2014 aims to spread the bidding process for firms applying for new 15-year rail franchise agreements.

The 8am, 8.30am and 9am Norwich to London services were cancelled yesterday after the main line was blocked after the power failure involving the 7.40am train.

A NXEA spokesman said a complete locomotive power failure was 'unusual' and the company was investigating the cause.

The problem was compounded after services in the Cambridge area were suspended because of cable thefts – disrupting those who sought an alternative for reaching the capital from Norfolk.

Chris Starkie, spokesman for the Norwich in 90 group, which is campaigning for quicker and more reliable rail services, said the new short-term operator was likely to be stuck with the old rolling stock for the next few years.

'The train breakdown shows the age of the trains and the carriages and highlights the need for more up-to-date equipment. It would be unfortunate if it happened during the Olympics but there has not been a train breakdown like this for a while,' he said.

The winner of the new short-term franchise is set to be announced next month. It will operate from February 2012 to July 2014 and give the Department for Transport time to draw up a 15-year contract in line with the findings of the McNulty report to reform the industry.

North Norfolk MP Norman Lamb said longer franchises would give operators greater incentives to invest in rail networks.

'We need investment in rolling stock and engine breakdowns are infuriating and reconditioned engines will never achieve the same reliability as new engines. We are all inpatient for improvements. It is frustrating, but I understand the need to phase the tendering process for the long franchises and makes it all the more important to get real improvements,' he said.

The delay over the start of a long-term Greater Anglia franchise comes after all 16 Norfolk and Suffolk MPs wrote to transport secretary Philip Hammond this week, lobbying for network improvements and calling for a 15-year franchise to begin as early as possible.

Norwich North MP Chloe Smith said it was always a possibility that the short-term contract would be extended by 12 months.

'My priority is to see full investment come to us as early as possible and it is more likely to come with a long franchise rather than a short one. It is a shame to have any delay to getting full investment. We strongly expect that the successful short-term franchise bidder will start making moves immediately towards improving services,' she said.

George Freeman, Mid Norfolk MP, said it was important that the Norwich-Cambridge line also received a major investment under the new franchise.

Rail services on the Norwich-London line were further delayed yesterday after a person was hit by a train at Shenfield, in Essex, There were delays of up to an hour and services resumed at 5.30pm.

adam.gretton@archant.co.uk

Only last Friday, prime minister David Cameron, in an interview with the EDP, recognised the importance of better rail links for Norfolk people

He was asked:

National Express are losing the franchise. There will be a short-term franchise holder put in and then a longer term one. It seems fair to surmise that if the short-term franchise holder does a good job they might be awarded the longer term. The short term franchise covers the Olympics and we must absolutely get our rail service running smoothly for that period. If there is one Olympic legacy for Norfolk it will be boosting the tourism industry and part of that will depend on a reliable rail service. With regards to the long-term franchise can you give us any assurance that in handing out the franchise there will be a commitment to investment?

He replied:

Yes, I can. The whole point of longer-term franchises for rail services is that you can then insist that the franchisee puts more money into services, to platforms and all the rest of it. That is absolutely essential. The rail link between Norfolk and London is vital and, as you say, if you are going to get the legacy benefit you need a faster service. So the point of a franchise is more investment. I think there are big opportunities for the Olympics and let me reassure you we are about to launch a massive campaign to encourage people to visit for the Olympics but also to go on visiting the UK after the Olympics is over. There will be a big advertising promotional campaign. We are also going to be working with hotels to try and co-ordinate great deals to encourage people to bring their families, to come back twice that year and the rest of it. We have a very active tourism minister in John Penrose and perhaps I should send him up here to tell you about it.