M4 relief road public inquiry 'will consider alternatives'
A public inquiry into the M4 relief road project is set to begin in the autumn and will consider "all alternatives" proposed, Economy Secretary Ken Skates said.
Mr Skates said the stretch of motorway could be opened by autumn 2021 if ministers go ahead after the probe.
A "fresh analysis" will be drawn up on the alternative "blue route" upgrade of existing Newport roads, he told AMs.
An environmentalist has promised to "dismantle" Welsh ministers' case.
Mr Skates said: "An independent Inspector will review the need for the scheme and consider all environmental, social and economic factors.
"They will hear evidence and examine the technical experts as well as hearing from supporters and objectors."
He said: "The historic consideration of options will be examined, as will all alternative routes proposed by objectors, including the much referred to 'blue route'.
"This will robustly test the merits of suggested alternatives and give an independent view on whether the proposed scheme offers the most sustainable, long term solution."
Mr Skates said the inquiry was set "to commence this autumn at the Lysaght Institute in Newport, with a pre-inquiry meeting taking place on 18 July".
"The inquiry itself is expected to take around five months, following which the Inspector will produce a report and recommendations to me," he said.
If the Welsh Government decided to proceed after the inquiry, "the new section of M4 could be opened by autumn 2021", he said.
Later Mr Skates said a "fresh analysis" of the blue route will be carried out prior to the inquiry but that strategic studies had shown that option would provide "very little relief" to the motorway and would worsen problems on local roads.
The Welsh Government's preferred "black route" is estimated to cost £1.1bn excluding VAT and inflation. It would involve building a new six-lane motorway south of Newport along the Gwent Levels.
That proposal has provoked opposition from environmental groups warning of "ecological destruction on an unprecedented scale".
Some Labour AMs are in disagreement with the plans, as is Plaid Cymru, which is backing the blue route.
Alun Cairns, Secretary of State for Wales, welcomed the announcement saying he looked forward to a quick inquiry: "The sooner we can establish the route and deal with outstanding concerns, the better."
Dai Lloyd of Plaid Cymru said: "The truth is that we do need a solution, and I don't think that doing nothing is an option for people in that local area or the business of south Wales.
"I welcome the intention to look at a broad range of options in an entirely independent enquiry," saying he would also like the inquiry to look at the abolition of the Severn Bridge tolls.
Gareth Clubb, director of Friends of the Earth Cymru, said earlier: "We'll be providing evidence that dismantles the Welsh Government's case."
He said the group would ask why the Welsh Government had not acted on its own previous analysis "that 5% of peak traffic could be stripped out of the Brynglas Tunnels by partial closure of one motorway junction".
He added: "We're looking for a public inquiry to be rigorously independent, with an inspector who's not afraid to tell the Welsh Government some unpalatable truths."
"The inquiry needs to look at the whole range of issues to uncover the feeble evidence on which the Welsh Government is pinning its case, the shaky rationale for the project, the massive cost," he said.
The inquiry is expected to begin in the autumn.
The announcement comes as 18 months of nightly closures of the Brynglas tunnels in Newport begin for maintenance work.