The Welsh Labour Government’s plans for a new stretch of M4 are a costly mistake.

Despite mounting evidence that the scheme is a slow, ineffective and expensive attempt to deal with the problem of the traffic bottleneck on the M4 around Newport, the Government has committed to developing the so-called ‘black route’ of a new road that will cut through our precious Gwent Levels.

This week, Plaid Cymru obtained information that the Government will have spent almost £20m this year on preparing the way for a new M4, even though the scheme has yet to be given the go-ahead and despite their promise last year not to spend any more money on it.

This is almost three times as much as they initially estimated.

With spending already escalating before construction has even begun, I wonder what the final cost of the road will be. It is currently expected to cost us £1 billion by the time it is completed, a staggering amount which will blow all of Wales’ borrowing powers on just one scheme.

If they can’t get their sums right at this stage, how can we trust they’ll get their sums right over the years of building ahead?

I understand that improvement is desperately needed on the stretch of M4 around the Brynglas Tunnels. The road cannot cope with the weight of the traffic and this strangles economic development in South Wales.

However, businesses and travellers will have a long time to wait for any improvement, the Government’s favoured ‘black route’ will take 15 years to be finished. That’s 15 years of road works and disruption.

There are also concerns about the impact the new road will have on the port of Newport. Associated British Ports has invested many millions of pounds in Newport and it is an important part of the town’s economy with 3,000 jobs relying on the port. The director of the port has claimed that it could cost them £30 million in investment.

The plan will also cause irreparable damage to the Gwent Levels, an ancient area of international significance for its wildlife and for being one of the largest surviving areas of ancient grazing marshes and drainage ditch systems in Britain. The whole area is a designated Site of Scientific Interest.

It is time for the Government to accept that they are making a huge mistake. Most AMs, including most Labour backbenchers, are fiercely opposed to the planned route. Unfortunately, instead the Government seem to be going full throttle with their spending on this deeply unpopular scheme.