A Freedom Of Information response reveals that the Welsh Government paid London-based engineering consultancy Arup more than £6.3m from 2010-2011 to advise on the controversial project to divert the M4 round Newport through a SSSI.
Eluned Parrott, the Welsh Liberal Democrat transport spokeswoman said the “billion pound mistake” would see Welsh finances “tied up for a generation”.
“It looks increasingly likely that these plans are doomed, so it's time for the Welsh Government to stop wasting public money on it,” she said.
“It’s particularly insulting for taxpayers that not only has £6m already been spent drawing up plans for this road since 2011, but to add insult to injury, the Welsh Labour Government has evasively refused to publish the full conclusions of this expensive, yet flawed, consultation.
“In budget negotiations, the Welsh Lib Dems agreed that no construction of the M4 relief road will start before the next Assembly elections, and that no construction contract would be awarded.
“The deal means that no irreversible decisions on the M4 can be taken before then, but given the number and cost of the hurdles that need to be overcome, and the enormous environmental damage it would do, surely the best idea would be to shelve it, permanently, now.”