'Ulez for motorways' at risk of being rolled out in Wales

However, Mark Drakeford's administration stressed it has no plans to use such powers.

Welsh Conservatives lost an attempt to remove the powers from the Environment Bill during a series of Senedd votes.

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Labour and Plaid Cymru Senedd Members joined forces to defeat the Tory amendment on Tuesday night.

A separate attempt to reduce a harmful gas created by vehicle engines through targets was also defeated.

Cardiff Bay could only impose charges on the Welsh trunk road network, including the M4 motorway and major A roads.

The power is also only permissible in limited circumstances.

The bill would alter the rules to enable the Welsh Government to charge drivers to enter clean air zones anywhere on the network.

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The Conservatives' Shadow Climate Change Minister Janet Finch-Saunders said: "In some instances that [public transport] isn't an option and cars are the only option."

She also lamented Drakeford's administration for its "failure to adequately support public transport".

Climate Change Minister Julie James stressed there were "no current plans" to impose charges on trunk roads.

The Swansea West MS also highlighted how clean air zones were "a precautionary retained measures which could be introduced on certain roads if other measures prove insufficient to meet our obligations".

However, the M4 at Newport and a stretch of the A470 near Pontypridd have been earmarked as potential zones.

The speed limit has already been cut to 50mph in both places in an attempt to reduce the amount of nitrogen dioxide (NO2) in the air.

Speed-reducing measures have proved controversial since Drakeford cut limits to 20mph in places.

However, documents from Cardiff Bay argue clean air charges will only be considered if there is not a long-term reduction in the amount of NO2 emitted from vehicle exhausts.

Opposition parties tried to amend the bill to also include targets on NO2.

The move was defeated after the presiding officer casting a deciding vote following a tie.

Plaid Cymru MS Delyth Jewell had claimed legally-binding NO2 targets were "crucial for safeguarding human health in Wales".