Osborne: M4 bottlenecks are 'damaging the Welsh economy'
The chancellor has told BBC Wales that the M4 in south Wales is one of the worst traffic bottlenecks in the UK and it is damaging the Welsh economy.
George Osborne, visiting south Wales, said the Welsh government had the powers to start work immediately.
He said he had travelled on the motorway on Monday and there were "the usual traffic problems".
"It's not been dealt with for years and years and is damaging to the Welsh economy," he said.
Mr Osborne has previously promised to work with the Welsh government to sort out congestion in the Newport area.
Options include a new three-lane motorway route to the south of the city.
Mr Osborne told BBC Radio Wales: "I've spent the night in Cardiff but yesterday clearly, on the M4, there were your usual traffic problems.
"It's one of the bottlenecks for the entire United Kingdom and, again, not dealt with for years and years and years, and damaging to the Welsh economy."
He told BBC Radio Wales that while recent reforms would give the Welsh government more borrowing and tax powers, the UK government did not want to wait for the legislation to pass.
He said: "We don't want to wait for those borrowing powers to be in place, we want the Welsh Assembly Government to get on and to be able to fund this earlier.
"Why wait for a vital improvement that will support jobs in the area?"
The Welsh government has previously been told it can use existing borrowing powers to fund the project.
Plans to ease congestion on the M4 in south Wales were first unveiled by the Welsh government in 2004.
Five years later the then Labour-Plaid coalition in Cardiff Bay shelved the idea when the estimated cost rose to £1bn.
In April, Mr Osborne confirmed his backing for an M4 relief road, saying it was one of the most important road schemes in the UK.
Later in November, UK ministers agreed Welsh ministers could borrow the money needed to fund the scheme.
During his interview with BBC Wales, the chancellor also spoke about the escalating row over funding which is threatening to delay a major upgrade of the Great Western main line between Swansea and London.
The dispute is over who pays for a separate electrification of railway lines in the south Wales valleys.
Mr Osborne maintained that the valleys lines work was mainly the responsibility of the Welsh government, which has said the UK government should foot the bill.
The chancellor said: "The deal was set out in 2012. There's a shared financing for the whole electrification process.
"The London to Swansea line, which obviously is principally the responsibility of the Westminster government, and then the valleys lines which is principally the responsibility of the Welsh government."