The Department for Transport has issued a fresh acknowledgement of the negative impact that the controversial Western Link road could have on the environment.

Civil servant Robert Fox, from the department, has written to local councillors reiterating some of the concerns about the scheme and stating that it is currently rated 'large adverse' - the second most extreme evaluation in the government's transport analysis guidance on biodiversity.

He was responding to a letter from opposition councillors from County Hall who are opposed to the proposed road, connecting the Northern Distributor Road to the A47 to the west of Norwich.

The Conservative-controlled Norfolk County Council wants the government to pay £168m of the cost, but late last year, members from opposition parties united to write to the DfT calling for them not to bankroll the route.

Members of the Labour, Liberal Democrat and Green groups signed the letter, in which they say the road, which would cost £50.8m per mile:

  • Undermines national climate change objectives

  • Damages wildlife habitats

  • Risks planning failure

  • Does not represent value for money

  • Is being handled in a way that is not transparent and lacks accountability

Last week Mr Fox, from the DfT, wrote to the councillors saying he could not get involved in the decision-making process at County Hall but reiterated some of the environmental impacts of the plans.

Mr Fox said he was grateful for their comments on the biodiversity assessment provided by the council, which gave a 'neutral' evaluation.

He said: "This issue has been raised with the council and they have confirmed that the rating was given as it factors in mitigation at both of these sites.

"It is worth noting that the summary assessment score for the whole scheme remains 'large adverse.'"

He also said the council will have to prove ecological mitigation in its planning application - which will be heard by County Hall itself.

Mr Fox also said that if the scheme - currently at the outline business case stage - progresses on to the full business case stage the council will have to release an assessment of the 'embodied carbon' in the project.

Embodied carbon is all the emissions resulting from the project, including producing and transporting materials and building the road itself.

On the scheme's value for money, Mr Fox said their concerns had been noted and would be considered in the DfT's review.

Responding to the DfT's letter, Green Party councillor Jamie Osborn said: "The response from the DfT confirms that there is no way the council can mitigate the damage to irreplaceable habitats that the Western Link would bring.

"The county council have been trying to manufacture evidence to back up their view of the road and its environmental impact, but their claims are rapidly falling apart.

"Instead of pursuing this harmful road even further and throwing good money after bad, the county council should start seriously investing in 100pc clean public transport with all the environmental and social benefits that would bring."

This was echoed by deputy Labour leader Emma Corlett who said the 'large adverse' impact makes it difficult for the council to get "this reckless scheme through planning".

She said: "If, as anticipated, the presence of the larger barbastelle bat colony leads to the location being designated a Site of Special Scientific Interest that would increase the environmental impact to 'very high' which would make the risk of planning failure even higher."

Highlighting the price of the project, Ms Corlett said costs could spiral even higher due to rising material prices and labour shortages.

She added: "The county council need to urgently work with local parish councils on a 'plan B' to address rat-running.

"This is possible in a far shorter time, cheaper and more sustainable way than concreting over ancient woodland and rare, protected species."

But Martin Wilby, Norfolk County Council's cabinet member for highways, infrastructure and transport remains confident that the road will go ahead.

He said: "The DfT make the point that the outline business case process, which makes the case for funding, and the planning process, around getting permission to build a road like this, are separate.

"We are taking our environmental responsibilities very seriously and are basing our proposals for the project, including our environmental mitigation measures, on evidence and national guidance."

Mr Wilby said he was confident the council will demonstrate through the planning application it can mitigate or compensate environmental impacts and create habitats for wildlife.