More than 400,000 schoolchildren are being taught by unqualified teachers, according to research revealed by the shadow education secretary, Tristam Hunt.

Labour’s education spokesman has made the issue of ending the use of unqualified teachers one of his central campaigns and this is the first time he has put a figure on the extent to which they are being used in schools.

Michael Gove, the former education secretary, introduced the right for free schools and academies to use unqualified teachers in 2012.

Labour claims the use of teachers who are not qualified leads to children in state schools being taught by people who have had no guaranteed training in safeguarding children, controlling a class or adapting teaching to respond to the strengths and needs of all pupils.

Hunt said there were 17,100 unqualified teachers in state-funded schools – a rise of 16% in the past year. The number in academies and free schools rose by 50%. In November 2012 , there were 5,300 unqualified teachers in academies, technology colleges and free schools, according to Department for Education figures, but the number has since risen to 7,900.

Hunt said 430,000 children were being taught by unqualified teachers, based on a class size average of 25.3.

He said: “David Cameron’s decision to allow unqualified teachers to be permanently employed in schools is seriously threatening standards for hundreds of thousands of children – and the figures are rising.

“Labour will reverse the unqualified teachers policy and put teaching standards first, with our ambition of a world-class teacher in every classroom. We will ensure that all teachers become properly qualified, continue to build their skills and are able to pursue new career pathways that keep the best teachers in the classrooms.”

Hunt promised that a Labour government would ensure all permanently employed teachers were qualified and claimed Gove changed the rules despite massive polling evidence showing the reform was unpopular with parents.

Gove argued that the change would make up the shortfalls in subjects such as computer science, engineering and languages, bringing state schools more in line with private schools where qualified teacher status is often desirable but not mandatory.

Gove’s successor, Nicky Morgan, has set about rebuilding relations with teachers, but has not yet indicated she will drop the policy. However, a Gove-commissioned review into initial teacher training would provide a possible route to removing one of Hunt’s effective lines of attack.

He claims Cameron is increasingly isolated on this issue and refuses to listen to the concerns of education experts, who describe the policy as retrograde.

In June, the Liberal Democrats finally broke with their Tory coalition partners on the issue and gave a commitment that its manifesto would require all teachers to be working towards qualification or be qualified.

Sir Michael Wilshaw, the chief inspector of schools, has said that unqualified teachers should be accredited as soon as possible after their appointment.

Chris Husbands, the director of the Institute of Education, said the decision to remove the requirement for teachers to gain qualified teacher status in state-funded schools “flies in the face of evidence nationally and internationally”.