In letters they said the proposed HS2, which could ultimately be extended to Scotland, 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 that Britain’s “poor infrastructure” is a “major obstacle” to long-term growth.
With just 70 miles of high-speed rail track, they said 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,” said the signatories.
Meanwhile, a group of economists said HS2 would support the creation of up to one million British jobs and give an “immediate boost” to the British construction industry.
They added: “Economic studies show 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.”
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.
The union bosses said: “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.”
Transport Secretary Justine Greening will make a decision on whether to press ahead with the scheme.