Newport M4 relief road plan 'unlawful', say environmental groups
Plans for a £1bn M4 relief road across the Gwent Levels are unlawful because they do not include any "reasonable" alternatives, say environmental groups.
The Welsh government put proposals for a new motorway south of Newport out to consultation in September.
But Gwent Wildlife Trust and Friends of the Earth Cymru says they ignore half a dozen other options including upgrading a road through a former steelworks.
The Welsh government said other options did not offer "a long-term solution".
Ministers have said that cutting motorway congestion in the Newport area is essential for the Welsh economy.
The main element of the new plan is for a section of three-lane motorway between junction 23 at Magor and junction 29 at Castleton.
The draft plan also has two "reasonable alternative" routes and another option which considers the consequences of doing nothing.
A 12-week consultation period closes on 16 December but the charities want the consultation to be re-run.
They say it is unlawful as the two "alternatives" offered were only different versions of the Welsh government's "single-minded" preference for a motorway route.
The consultation could include six or seven alternatives, they say, including ones previously suggested by the Welsh government.
In particular, they say it should include a proposal to be unveiled on Monday which suggests upgrading the dual carriageway through the former steelworks site in the city.
Friends of the Earth Cymru director Gareth Clubb said the situation now was similar to the challenge the charities made last year over the environmental impact assessment for the motorway proposals.
He said: "Because the consultation is not as comprehensive as it should be in our opinion, we hope the Welsh government will take the same action as in January and re-consult.
"The Welsh government does not appear to have a reason for limiting the options to simply a road across the Gwent Levels.
"We would have no option but to support or not support a very new major road. We think that that's unlawful.
"We want the Welsh government to either withdraw the consultation or persuade us of the merits of its limited range.
"If the Welsh government thinks the consultation stands, but we're not persuaded, a judicial review is an option we will consider."
Mr Clubb said the proposals to be detailed on Monday would deliver the Welsh government's aims "at a fraction of the cost and does not have lanes going over five Sites of Special Scientific Interest".
Plans to ease congestion on the M4 in south Wales were unveiled by the Welsh government in 2004.
Five years later the then Labour-Plaid coalition in Cardiff Bay shelved the idea when the estimated cost rose to £1bn.
In April this year, Chancellor George Osborne confirmed his backing for an M4 relief road, describing it as one of the most important road schemes in the UK.
UK ministers announced in November that Welsh ministers could borrow the money needed to fund the relief road.
Gwent Wildlife Trust has been campaigning against proposals for the relief road which it claims could destroy habitats and "create a barrier" preventing the movement of wildlife on the Gwent Levels.
The trust said the area was a nationally important location for wildlife.
A Welsh government spokesperson said: "We are currently consulting on options to improve the M4 around Newport. The closing date for responses is 16 December.
"Other options had been previously considered but were not taken forward in this consultation as they would produce very little relief to motorway congestion and not provide a long-term solution."