In letters to the Financial Times, Daily Telegraph and the Guardian, they said the proposed HS2 would boost growth and create jobs.
The final decision on whether to go ahead with the controversial rail link has been postponed until this month.
Signatories including John Longworth, director general of the British Chambers of Commerce, argued in the Telegraph that Britain’s “poor infrastructure” is a “major obstacle” to long-term growth.
With just 70 miles of high-speed rail track, they say the UK lags behind other “world-class” economies such as France and Japan, and is also trailing Morocco, which has 422 miles, and Saudi Arabia, with 342.
“The absence of a high-speed rail line connecting the northern parts of Britain to London and the European Union is a continuous embarrassment to those promoting British business overseas,” they told the newspaper.
Writing to the Financial Times, a group of economists said HS2 would support the creation of up to 1million British jobs and give an “immediate boost” to the British construction industry.
They added: “Economic studies show that effective modes of transport, including high-speed rail, enable entrepreneurs to get their goods and services to market in a secure and timely manner and facilitate the movement of workers to the most suitable jobs.”
In the Guardian, signatories including Bob Crow, general secretary of the RMT, and Frances O’Grady, deputy general secretary of the TUC, urged the Government to ignore the “wealthy ideological opponents” of HS2.
They said the planned line would immediately bring thousands of engineering and construction jobs to the UK, as well as jobs long-term in the rail industry and regional employment.
The union bosses added: “HSR has been proven as an effective low-carbon mode of transport, creating a stronger economy, a boom for employment and a higher quality of life.
“Simply put, the UK cannot afford not to invest in HSR.”
There has been much support and also bitter opposition to the HS2 scheme, that would see a brand new high-speed line built from London through picturesque Tory heartlands to Birmingham.
The 100-mile rail link, due to be constructed between 2016 and 2026, aims to cut the London-to-Birmingham journey time to 49 minutes.
A second, Y-shaped route taking the line north of Birmingham to north-west and north-east England and on to Scotland is envisaged once the London-Birmingham route is completed around 2026.
The entire cost of the project is expected to be £32bn.
Transport Secretary Justine Greening had been expected to make a final announcement before parliament rose for its Christmas break.
But the decision was delayed until the New Year, with Ms Greening understood to be considering whether a £500 million tunnel should be bored to minimise impact on the Chiltern Hills landscape.
TaxPayers’ Alliance director Matthew Sinclair said: “While rich special interests are lining up to defend the multi-billion pound high speed rail scheme, surveys show that most of the public and most businesses would rather do something else with the huge amount of money it is going to cost them.
“Taxpayers can’t afford the thousand pounds a family that the new line will cost. With so many pressures on the public finances the Government should reconsider this enormous white elephant.”