POLITICIANS have been given more time to respond to a letter from an environmental campaign group opposing the planned Newport M4 relief road route.

Friends of the Earth Cymru wrote to Welsh Government two weeks ago to oppose the £1billion "black route" through Newport Docks on environmental grounds, citing a lack of consideration of other routes, and warning that they were prepared to take the matter to a judicial review.

Newport is set to get the new M4 road to relieve congestion by 2022 after Cardiff Bay politicians debated and agreed on the plan earlier this year.

Welsh Government had a fortnight to respond to the letter, which sets out why Friends of the Earth Cymru believe the government had not acted lawfully, namely that they have not consulted on a "substantive range" of options.

The letter is a "pre-action protocol" to a judicial review from their lawyers Deighton Pierce Glynn.

It claims that Welsh Government, in looking at a new motorway south of Newport and two variations "unlawfully limited the range of reasonable alternatives" including a "blue route" along the existing A48 and enhanced public transport.

The deadline has now been extended by another week at Welsh Government's request, after which Friends of the Earth Cymru will have four weeks to consider whether they will go ahead with legal action.

In return Welsh Government has agreed that they will not pursue a legal argument suggesting that the group caused "undue delay" in deciding whether to bring the matter to a judicial review, something which is often cited in such cases, said director of Friends of the Earth Cymru, Gareth Clubb.

A spokesman for Welsh Government said he had "nothing to add".

Speaking to the Argus earlier this month, Mr Clubb told the Argus that traffic projections on which the relief road scheme is based are "wildly inaccurate".

Transport minister Edwina Hart previously said the black route was chosen following consultation and would involve reclassifying the existing M4 between Magor and Castleton; connections with the M4, M48 and B4245; and cycle- and pedestrian-friendly infrastructure.

The owner of Newport docks, Associated British Ports has already claimed that trade could be "severely affected" by the route.

Discussion of a relief road to cure the traffic bottleneck at Newport has been going on since 1991, when Welsh secretary David Hunt announced a new motorway would be built.

In June this year shadow economy minister Rhun ap Iorwerth AM called on Welsh Government to rule out the black route on environmental and financial grounds and instead upgrade the existing A48.