Image copyright Wales Office Image caption New hybrid trains on the line will look like this

An inquiry will be held into the scrapping of rail electrification plans for the main line between Cardiff and Swansea, MPs have confirmed.

In July, the transport secretary said faster journeys between the cities would be achieved with new trains.

Chris Grayling said the new fleet would be on the line from the autumn.

On Thursday, Welsh Affairs Committee chair David Davies said the probe would consider if "claims of greater capacity and quicker journeys stack up".

The new trains will be bi-mode, meaning they can run on both electrified and non-electrified sections of track.

Network Rail is working to ensure electrification between London and Cardiff by December 2018.

Image caption David Davies was re-elected unopposed as committee chair in July

Mr Davies said: "The government has decided to cancel plans to electrify the route between Cardiff and Swansea, and instead announced investment in new rolling stock and station improvements.

"We have launched this inquiry to examine the reasoning behind this decision.

"Do their claims of greater capacity and quicker journeys stack up, or could it be argued that electrification would provide better value for money?"

Mr Davies, Conservative MP for Monmouth, said the investigation would also consider the impact of the decision on the south Wales economy, whether it reflected Wales' transport priorities and also whether further powers over rail should be handed to the Welsh Government.

'Disruptive'

The UK government said passengers would have "faster, modern trains with increased capacity, greater comfort and better connectivity from this autumn".

A spokesperson added: "Journey times between London and Swansea will be cut by 15 minutes and we are also looking at direct services from Pembroke Dock to London via Carmarthen and station improvements at Cardiff and Swansea.

"Secretary of state for Wales, Alun Cairns affirmed his commitment in July to exploring the possibility of a new Swansea Parkway Station north of the city and supporting proposals for Wales' first privately run station at St Mellons.

"Disruptive electrification works between Cardiff and Swansea will no longer be needed because the new fleet of trains will be doing the route in exactly the same amount of time as they would be on a fully-electrified route."