Commonly known as Butterfly Bush, the buddleia is growing out of cracks in the brickwork of the East Coast Main Line bridge that crosses the River Nene.

As pretty as it may be, railway enthusiast Rev Richard Paten believes the shrub is a glaring example of "neglected maintenance".

But Network Rail says that is not the case and the plant has bloomed because Peterborough has seen plenty of rain in recent months.

Mr Paten, who founded Nene Valley Railway and purchased the line's first steam locomotive, which was named City of Peterborough, said: "It may only be a buddleia, but that buddleia is a symbol of the relative lack of investment in the East Coast Main Line in Peterborough. Its presence implies that the viaduct is poorly maintained.

"Not only is it a potential safety issue, but it does not inspire confidence in the city. At a time when we are trying to encourage greater use of the railways and less of cars, it does not give much confidence when people see the lack of maintenance of what is Britain's second most important train line."

Rev Paten, who is the founder and chairman of nearby Railworld, added: "Railworld is trying to promote a 21st century rail showcase and sustainable transport centre, as well as having plans to develop a TransEco centre. The 'buddleia line' is a poor gateway for those developments."

The buddleia first appeared in the same place in 2004 when Rev Paten claimed the bridge would not look out of place in a "poverty-stricken country".

A spokesman for Network Rail said: "Recent high rainfall across the region has accelerated the growth of vegetation in and around the local area.

"This bridge will be inspected shortly, as part of Network Rail's ongoing maintenance programme, and then appropriate remedial measures will be taken.

"If any member of the community has a concern over the condition of any rail assets that we own and manage, we encourage them to contact the Network Rail National Helpline directly on 08457 11 41 41."