The plans would have seen a 14-mile motorway built as a gateway into south Wales in a bid to tackle the congestion faced by motorists around Newport between Junctions 24 and 28.

First Minister Mark Drakeford's decision to scrap the six-lane scheme follows a public inquiry overseen by planning inspector Bill Wadrup, who said the case for the road had been "compelling."

It is the third time Welsh ministers have shelved plans for the M4 relief road, which had been supported by Mr. Drakeford's predecessor Carwyn Jones. An estimated £44 million was spent on a public inquiry and other development costs.

Tom Watkins, associate director in the South West and Wales industrial and logistics team at global real estate advisor Colliers International, says the decision will hinder economic growth in Newport, South Wales and the West of England.

“It’s really disappointing to hear that the Welsh ministers have ruled against the relief road. Traffic on the M4 around Newport is incredibly prone to heavy congestion at certain periods of the day, particularly with the increase in traffic flow over the Severn Bridge since the scrapping of the tolls.

“Newport has the potential to become a major logistics hub due to its labour supply, and theoretical proximity to the national motorway network, however it’s widely known by both commercial and domestic drivers that this stretch of the M4 is notorious for congestion. From a logistics perspective, distribution occupiers are now so focused on efficiencies and small margins that the heavy traffic could deter inward investment from these national and international companies.”

“Furthermore, the new M4 relief road had the potential to unlock development opportunities, which would have positively impacted the area, but I can see this decision being a major stumbling block to the growth of the city.”