Any decisions on future schemes would be taken following the spending review.
Tolling the M4 in Wales would be a matter for the Welsh Assembly.
More top news
One person has been confirmed dead and several are injured in the ongoing incident in Las Ramblas.
A number of fatalities and several injuries have been reported after a van has crashed into people in the Ramblas area of Barcelona.
John Underhill said geological changes 55 million years ago mean the UK's geology is unsuitable for shale oil and gas production.