HS2 plans for one of the longest viaducts in the UK have been revealed - but campaigners say concerns over the proposals have been "ignored" by the government. 

HS2 Ltd has revealed an outline concept for the Colne Valley viaduct, which programme director Mike Hickson said will be one of HS2's "best known structures".

The 2.1m long viaduct will cut through the Colne Valley Regional Park, which consists of more than 40 square miles of farmland, woods and waterways to the west and north-west of London, including in Denham and Chalfont.

The plans have been criticised by Stop HS2 campaigners, who say that local concerns have been ignored. 

A statement on the Stop HS2 website said the plans were "just another puff piece, which very much focusses on the passenger, who will be across the viaduct in moments, and ignores the local community who have to live with it." 

They said: "Take noise barriers: you might think that reducing noise for the local area is the most important function of noise barriers. But the very first paragraph mentioning them is all about the views for the passengers:their effectiveness seems very much an afterthought.

"Similarly local concerns about the gantries are ignored. Referred to in most of the documents as OLE posts (a much prettier name for “Overhead Line Equipment”), the documents leaves it up to others to design them.

The only detailed picture of the gantries is the view from the train, with the caption helpfully pointing out that for the passengers travelling at 340kph 'motion blur makes the vertical elements of the edge condition almost completely invisible, achieving an unobstructed view of the Colne Valley.' 

"Interestingly, there is no water in the view from the train, just a green blur. There is no acknowledgement for people outside the train, the gantries could be ugly and prominent, a problem which has afflicted other rail schemes in England." 

Sadie Morgan, chair of the Independent Design Panel, said the design was "imaginative and carefully considered". 

She said: "The Independent Design Panel will continue to work hard to ensure that the viaduct’s final design respects its location and communities, whilst being a shining example of great design that Britain can be proud of."