Birmingham: 46mins, down from 1h 22mins
Liverpool: 1hr 23mins, down from 2hrs 8mins
Manchester: 1hr 6mins, down from 2hrs 7mins
Edinburgh: 2hrs 9mins, down from 4hrs 23mins
Glasgow: 2hrs 16mins, down from 4hrs 10 mins
Source: Network Rail
A £34bn high-speed rail network planned from London to Scotland should connect to similar lines already in Europe, city officials have said.
Leaders from 11 UK cities have backed plans which would cut journey times.
They say London to Manchester journey times could come down to one hour 13 minutes and London to Scotland trips could be made in under three hours.
Manchester City Council leader Richard Leese said the UK's railways have "not kept pace" with the growth of cities.
Network Rail, which owns and operates Britain's rail infrastructure, estimates journey times could be even faster.
The cities involved are Birmingham, Bristol, Cardiff, Edinburgh, Glasgow, Leeds, Liverpool, Manchester, Newcastle upon Tyne, Nottingham and Sheffield - although their leaders have not put forward an actual route for the line.
A British high-speed line could carry up to 15,000 passengers per hour each way between London and other major cities, with double-decker trains offering the potential to almost double this figure.
Over 60 years, it is estimated that the line could save 30 million tonnes (29.5m tons) of CO2 worth £3.2bn by diverting passengers from air travel to rail.
Mr Leese, who is chairman of the high-speed campaign, warned: "We cannot continue to grow the UK's economy and compete on a global stage without a high-speed rail network in the UK.
"There are 3,480 miles of high speed railway lines in mainland Europe with a further 2,160 miles under construction and 5,280 miles planned for the future.
"In Britain, despite inventing the world's first passenger railway we only have 68 miles (the Channel Tunnel High Speed One link) in operation."
The government has already set up an organisation, High Speed Two, which will study the possibility of a north-south high-speed line. Network Rail has outlined its high-speed vision for the future, with 200mph (322km/h) trains.
Politicians from across the major parties have welcomed the campaign.
Transport Secretary Lord Adonis said: "These cities should be congratulated for working together to secure the economic and environmental benefits that high-speed rail (HSR) could bring."
Shadow transport secretary Theresa Villiers said: "The Conservatives have long been aware that the argument for HSR goes beyond faster journey times to London, and covers a transport revolution focused on connecting some of our great British cities outside the south east."
Liberal Democrat transport spokesman Norman Baker MP said: "Britain desperately needs an HSR network to bring it up to European standards. We cannot hope to become a low-carbon economy unless we invest for the long term in decent public transport infrastructure."