Communities must not be split, Norfolk MP Richard Bacon has said as Network Rail indicated it is drawing up plans to close level crossings between Norwich and London.

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The South Norfolk politician said any proposals would have to include a bridge or a tunnel to ensure drivers were not forced into long de-tours as a result of the upgrade.

Network Rail, which is in charge of the country's rail infrastructure, has said it is looking at whether level crossings could be closed as part of its blueprint to cope with growing demand for rail services over the next 30 years, but work has just started and the crossings under threat are not expected to be revealed until the summer.

The Chancellor pledged in the Autumn Statement to speed up the line between Norwich and London, and Network Rail is already working on upgrades to the track to speed up the line.

Mr Bacon said that while he was all for having trains that get to their destination faster, the most important thing was that the service was reliable, and arrived when it said it would arrive.

He also said he did not want to see fewer trains stopping at Diss.

'Any changes should not result in a poorer service,' he said. 'You shouldn't do things that split communities. The only reason level crossings were installed is because they were running a railway line through a community. You can't suddenly say you can't use this road. People won't wear it. They might not be trunk roads, but to people locally, they are critical. My concern would be to ensure it doesn't happen. If they are suggesting the closure of any crossings, they must make suitable alternative, not an eight mile dogleg journey. The obvious answer is you dig a tunnel or you build a bridge. It may be inconvenient, but it would be inconvenient for those having to make a de-tour if you don't.'

A Network Rail spokesperson said: 'Britain has one of the safest railways in Europe but level crossings remain a risk that we need to tackle.

'Closing a level crossing is always about improving safety but in some cases, like on the line from Norwich to London, it will also help us to achieve faster journey times.

'We always look at how we can provide an alternative means for people to get across the railway when we consider closing a crossing. This project is very much at an early stage and in about six months we will have a clearer idea of what level crossings will be affected. We plan to consult on our initial plans and will listen to the views and experiences of people across Essex, Suffolk and Norfolk.'

Chloe Smith, who has headed up the rail taskforce to improve the line between Norwich and London, said: 'The taskforce has begun the work of looking at all the level crossings along the Great Eastern Main Line, in Norfolk, Suffolk and Essex, because some of the older crossings slow the line down. Clearly safety and rights of way remain paramount and the work is to see if in some cases there may be an acceptable alternative to having a level crossing which slows the line. It's very early days of that work.'