The public body, which conserves and enhances the Chilterns Area of Outstanding Natural Beauty (AONB), made the statement after a sinkhole appeared above HS2’s Chiltern Tunnel on Saturday.

In a statement on its website, CCB says that in a report published by the Chiltern Society in 2010 geologist Dr Haydon Bailey outlined the potential impact of tunnelling, including a risk of ground collapse in areas with deep sections of weather chalk.

“Despite confident assurances by HS2 Ltd throughout the Select Committee process, proceeding approval of the HS2 Bill, and repeated assurances by their contractors since, the Chiltern Society, the Chilterns Chalk Stream Project, the Chilterns Conservation Board, and many local groups and individuals have continued to express their concern that tunnelling operations will be extremely damaging. Unfortunately, our fears appear to be justified and we will now be urgently seeking answers and for appropriate action to be put in place to safeguard the landscape, wildlife and residents of the AONB,” the statement says.

HS2 told T&TI on Monday that investigations were ongoing but the sinkhole, which is above a completed section of tunnel, was likely to be linked to pre-existing ground conditions above the tunnels”.

HS2’s main works contractor, Align – a joint venture of Bouygues Travaux Publics, Sir Robert McAlpine, and VolkerFitzpatrick – is responsible for the Chiltern Tunnel. At 16km in length, it is the longest tunnel on the high-speed rail line.