A review into the current state of the National Cycle Network has found nearly half of routes around the country are unsafe for 12-year-olds.

A report published by cycling charity Sustrans on the 16,575-mile network revealed more than half, 57pc, of the UK population lives within a mile of its paths but poor surfaces and barriers are preventing access for users.

The charity said it is working with local authorities to create accessible traffic-free routes and called for increased funding to improve unsafe sections of the network.

Norfolk County Council said it agreed that investment brings many benefits, adding: 'We've seen the huge surge in cycling in the city since the £15m Department for Transport investment in the Norwich pedalways.

'And we're very pleased to have recently secured £1m for our Greenways project which aims to open up even more of Norfolk's disused railway lines to create attractive traffic free routes for people to use get to work, to school and for leisure.'

Sustrans routes in Norfolk include Marriott's Way, which takes cyclists on a 26-mile route between Norwich and Aylsham.

Just over a third of the paths on the network nationally, 32pc, are separated from motor traffic but on-road sections still account for 68pc of the routes.

The review by Sustrans also showed only 54pc of routes are currently suitable for a 12-year-old to use safely, a road safety benchmark set by the UK government.

Avid cyclist Tony Clarke, 78, who is a board member of British Cycling Eastern Region, said Marriott's Way suffered poor surfacing but that it was accessible from the city in King Street and is a popular journey for families and tourists.

'It's a pretty good route, there are points where you struggle but you need the right bike for it,' he added.

A Norfolk County Council spokesman responded: 'There has been significant investment in the Marriott's Way as a cycling route, particularly between Thorpe Marriott and the city and we know this more urban stage is very well used by people commuting to work.

'Elsewhere the route is more rural and the surface and style of cycling reflects this.'