Students will be able to leave academic education at 14 in favour of vocational training at specialist colleges under coalition plans.

Up to 70 technical schools teaching practical skills could be opened before the next election, according to Lord Baker of Dorking, the former Tory education secretary who is heading the scheme.

Baker said the schools were not a small experiment but a movement designed to tackle a shortage of young people with vocational skills.

"If we are going to have high-speed rail, the fastest broadband in the world, new nuclear power stations, we are going to need technicians," he told the Times. "We simply don't have enough technically orientated people coming through."

Critics fear it would create a two-tier system, with less able students at risk of being pushed into vocational courses and pupils forced to make important decisions about their future at too young an age.

Christine Blower, the general secretary of the National Union of Teachers, said: "It is not acceptable that at the age of 14 pupils may be forced into specific learning routes which could restrict their future education or career choices. Attempting to separate technical or vocational education from mainstream schools is socially divisive and will lead to a two-tier system with technical schools being seen as the poor cousin.

"The government needs to revisit the proposals put forward by Tomlinson and the NUT which call for a single overarching qualification that embraces all young people and does not label them as one thing or another at such a young age."

Baker insisted that 14 was a reasonable age to make choices about a career path. "Eleven is too soon to choose that, 16 is too late; 14 is the right age of transfer," he said.

The coalition has pledged to open technical schools, with links to employers, in at least 12 cities across the country.

Plans were under way for five to open by next autumn, and between 12 and 20 by September next year, Baker said. One, sponsored by the plant machinery company JCB, had already opened in Staffordshire.

Areas in which colleges are planned include Walsall, Hackney, Southwark, central Bedfordshire, Luton, Norwich, Wigan, Sheffield, Warrington, Daventry and Knowsley.

By 2013 all pupils in England will have to stay in education or training until the end of the school year in which they turn 17. By 2015 they will have to stay on until they are 18.

Baker's plans come after the former education secretary Estelle Morris said thousands more pupils would stay in school past the age of 16 if they took GCSEs at 14, with those more suited to practical courses starting to study them at that point.

They would be less likely to drop out of school or college, Morris told the North of England education conference in Blackpool yesterday.

The Labour peer, who was a teacher herself, joins a growing number of educationalists calling for GCSEs at 16 to be abolished. In November Professor Alan Smithers, the director of Buckingham University's centre for education and employment research, argued in a paper for the Sutton Trust that taking the exams at 14 and then choosing between academic, vocational or technical training routes would give pupils a better chance of a good job.