A TOP lawyer acting for the government admitted to the Supreme Court this week it is 'unarguable' the planned HS2 railway project would be environmentally damaging.

The Department for Transport has been taken to court by the Amersham-based HS2 Action Alliance after a judge previously ruled a failure to carry out a proper environmental analysis of the project was an 'egregious breach' of guidelines.

The campaigners' case is a full Strategic Environmental Assessment of the proposals should have been carried out before the government agreed to proceed with the plans.

Tim Mould QC, representing the DfT at the hearing, told the Supreme Court on Wednesday: "It is unarguable that high speed rail is environmentally damaging.

"It has never been disputed that upgrading existing lines is far less damaging environmentally."

Campaigners also say assessments of alternative routes to the main plans should also have been carried out and Mr Mould told the court: "It has always been our position that an upgrade of existing lines would be environmentally superior."

The HS2 Action Alliance believes that if the assessment had been undertaken then HS2 would not have been adopted in 2010.

The route of the line would cut through the Chilterns Area of Outstanding Natural Beauty, along with 24 Sites of Special Scientific Interest.

The panel of seven Supreme Court judges is likely to rule on the hearing next month. They can refer the case to the European Court of Justice for advice if necessary.