The government has started a five-month consultation exercise into the proposed high speed rail link between London and Scotland via Birmingham, Manchester, Leeds and Newcastle.
Transport Secretary Philip Hammond said the project would deliver around £44bn of benefits and would cut journey times between London and other major cities by as much as an hour.
Hammond said: "We must invest in Britain's future. High speed rail offers us a once-in-a-generation opportunity to transform the way we travel in the 21st Century and would help us build a modern economy fit for the future.
"Countries across Europe and Asia are already pressing ahead with ambitious plans for high speed rail, while some of our key rail arteries are getting ever closer to capacity. We cannot afford to be left behind – investing in high speed rail now is vital to the prosperity of future generations."
High speed rail could bring Birmingham within 49 minutes of London, and Manchester and Leeds within 80 minutes or less. Birmingham and Manchester would be less than 50 minutes apart and Leeds and Birmingham just over an hour. Travel from London to Scotland's major cities would take around 3 hours 30 minutes. Running 14 or more trains per hour, each with up to 1,100 seats and offering much higher levels of reliability than the existing network, high speed rail could shift as many as 6 million air trips and 9 million road trips a year on to rail.
The government hopes the increased speed, capacity and connectivity provided by a high speed rail network would "reshape our economic geography, regenerate our urban centres and help to bridge the north-south divide that has held us back in the past, allowing Britain to build a modern economy fit for the future."
The new network would also free up large amounts of space on the West Coast, East Coast and Midland Main Lines, allowing for an expansion of commuter, regional and freight services on these lines.
The Government estimates the cost of the complete 'Y' shaped network at £32bn and expects it to generate economic benefits of around £44bn and fare revenues of around £27bn over a 60-year period. The proposed network would be delivered in two phases – the first a line from London to the West Midlands, and the second the onward legs to Manchester and Leeds.
A direct link to Britain's existing high speed line, High Speed 1 – which runs from London St Pancras to the Channel Tunnel – is also proposed as part of the initial phase of the scheme, to allow travel from cities linked to the high speed network to the continent.
Subject to the outcome of this consultation, the Government intends to secure powers to deliver each phase of its proposed high speed network by means of the hybrid bill process. Construction of any new network would be expected to begin early in the next parliament, with the line to the West Midlands completed by 2026 and the legs to Manchester and Leeds finished in 2032-2033.
The consultation runs until 29 July.