It will become the second toll road in Britain - following the M6 in Staffordshire - and will run between junctions 23 and 29 of the M4 to relieve congestion on the outskirts of Newport.
The newspaper reports that the Chancellor will agree to guarantee loans for the building of the M4 relief road, but the devolved Welsh government will meet the cost - expected to be around £830 million.
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A fine and dry day with some warm sunshine in the afternoon, especially in the east.
Parents are more concerned about the cost of sending their children back to school than the price of school holidays, according to research.
The Barclays report calculates regional scores based on gross domestic product, working hours and average house prices.