Britain will spend £1.1billion to electrify more of its rail network to help cut carbon emissions and speed up journeys, the government said today.
Only a third of Britain's rail network is electrified, far less than other European countries.
The government said the proposals would help employment and industry including tourism and freight, boosting Britain's competitiveness with European partners.
Britain is battling its deepest recession since World War Two and unemployment is at its highest level for over a decade.
The government, facing an election within a year and trailing in opinion polls, has brought forward capital spending to try to hasten the recovery.
The lines between London and Swansea, in south Wales, and between Liverpool and Manchester in northwest England will be upgraded in the first major electrification project since the late 1980s. Diesel trains currently run on both routes.
Journey times between Manchester and Liverpool are expected to be cut to 30 minutes from 44. Trips from Swansea to London will be 19 minutes faster after the eight-year project.
"This is the biggest electrification programme for a generation and a vital part of our rail investment and carbon reduction strategies," said Transport Secretary Andrew Adonis.
"It will be of huge benefit to passengers who will gain from faster, cleaner and more reliable trains," he added.
The short-term cost of infrastructure company Network Rail's financing will be met by the government, and there will be no impact on other Network Rail investment programmes in the five years to 2014, the Department of Transport said.
The electrification programme will pay for itself over the long term through lower train leasing, maintenance and operating costs, it added.
FirstGroup operates the main franchise between London and south Wales and also runs trains between Liverpool and Manchester.
Northern Rail, owned by Serco Group Plc and Dutch NedRailways, also operates services between the two major northern cities. Both companies welcomed the plan.
"Lord Adonis's announcement is good news for our customers on these routes," FirstGroup Chief Executive Moir Lockhead said in a statement.
"The electrification of the Great Western Main Line will allow us to operate a very large proportion of customer journeys into and out of London Paddington with electric trains, which maximises the environmental, reliability and journey time benefits electrification can bring," he added.