Image copyright Welsh Government Image caption The Welsh Government has proposed building a new six-lane motorway south of Newport

A decision on whether to go ahead with an M4 relief road south of Newport will likely end up in the courts, a minister has told AMs.

First Minister Carwyn Jones is yet to decide whether the scheme should go ahead.

Assembly Leader of the House Julie James said Mr Jones had not seen a public inquiry report on the project, as lawyers consider its contents.

She said the decision will "almost certainly" face judicial review.

AMs were told the first minister, who plans to stand down from the role in two weeks time, still intends to issue the order to build the road, but Ms James acknowledged time for him to do that was running out.

She said it would be for his successor to award construction contracts.

Three Labour AMs spoke against the road, including Llanelli's Lee Waters who said it is now understood to cost £1.7bn, up from the £1.4bn previously estimated.

The Welsh Government has proposed to build a six-lane motorway south of Newport, but needs to take a formal decision following the public inquiry which finished earlier this year.

It intended that a debate would then be held in the assembly with a vote. That has been pencilled in for 4 December, but it remains unclear if it is taking place.

Image caption Julie James said time for the M4 decision is "running out"

On Wednesday the Senedd passed a non-binding Plaid Cymru motion calling for the next first minister to take the decision on the road.

It faced no objection from the Welsh Government. Julie James said the decision to actually enter into the contract to build the road would be for the next first minister.

But she said that it remained the intention of Mr Jones to issue the statutory orders, which give permission for the road to be built.

"You can see that the time for that decision is running out," she said, saying Mr Jones would need more than a "few hours" to read the report.

"But nevertheless, if this first minister is able to do that, then we think he should do that.

"If he's not able to do it, then he's not able to do it, then it will of course go across to the next first minister."

Image caption Lee Waters said it is understood that the road would cost £1.7bn

She added: "This is a process that will be subject to appeal and judicial review, almost certainly, and therefore the lawyers are very keen that the exact provisions - what is relevant, what is not relevant, what should be taken into account or should not be taken into account - are set out for the first minister in making the decision and in reading the report."

She said the inquiry report would be published when the order decision is taken.

Plaid Cymru's Rhun ap Iorwerth said: "We don't believe that it's acceptable for either the current first minister to take the blame for doing something unpopular and then to disappear off the scene, or to take ownership of this as some means of leaving a personal legacy."

Tory AM Russell George accused the government of dragging its feet over the issue.

"We have had the public inquiry, the inquiry has now presented its findings to the Welsh Government, so I'm disappointed that we, as AMs here, haven't had the chance to scrutinise those findings, either" he said.