A Welsh Government “unwillingness” to improve the M4 influenced a decision by Ineos to suspend plans to move jobs to Wales, a UK minister has claimed.
The firm said on Tuesday plans to build a new 4×4 vehicle plant in Bridgend had been put on hold.
UK government Welsh Secretary Simon Hart told MPs this “of course is a Welsh Government deal”.
Welsh ministers “unwillingness” and “inability” to upgrade the M4, he said, “influenced the Ineos decision”.
The Welsh Government announced it would not be building the new £1.6bn 14-mile motorway in June 2019, due to cost and environmental concerns, three months before Ineos revealed its Bridgend production plans.
A commission was established to look at alternative solutions to the problem of congestion on the M4 in Newport.
The plant would have been built next to the current Ford engine plant at Bridgend, which is to shut this autumn with the loss of 1,700 jobs.
The new factory was expected to create about 200 jobs initially to make the new all-terrain Grenadier vehicle.
It was hoped it could employ up to 500 people in the longer-term, and work to clear ground at the site had already begun.
The decision by Ineos to suspend its plans followed talks with Mercedes-Benz over the acquiring of their Hambach site in Moselle, France, Ineos has said.
Mr Hart was responding to a question from shadow secretary of state Nia Griffith in the Commons on Wednesday, who asked what the UK government would do to “retain, create and attract new green jobs.”
She said Bridgend was “reeling” from the Ineos threat to take jobs elsewhere and that firms faced “very fierce international competition.”
Mr Hart said this “of course is a Welsh Government deal” and that “unwillingness” to make improvements to the M4 relief road “have influenced the Ineos decision.”
Later, the prime minister said that the UK government would “unblock the Brynglas Tunnels”, often blamed for motorway congestion around Newport, with a “proper M4 bypass”.
Speaking at the weekly session of Prime Minister’s Questions, Boris Johnson said his government would “do the things the Welsh Government has failed to do.”
During his question session in the Senedd, First Minister Mark Drakeford said Wales’ Economy Minister Ken Skates had spoken directly to Ineos on Monday evening.
“Anything we can still do to persuade them of the merits of coming to Bridgend and the outstanding workforce that is available to them there, we will,” said Mr Drakeford.
Welsh ministers would “never give up on making that case, up until the point where that company makes a final determination”, he stressed.
Mr Drakeford was responding to a question from the Conservative Andrew RT Davies, who said “we should be working night and day to convince Ineos that Bridgend and the wider south Wales economy are an ideal home for their ambitious proposals for this new facility”.