More than half a million pupils in state-funded schools are being taught by unqualified teachers, according to new analysis by the Labour Party.
The number of unqualified teachers has risen by 62% to 24,000 since 2012.
Labour claim up to 613,000 children are taught by unqualified teachers, assuming an average class size of 25.5 children.
Shadow schools minister Mike Kane, a former teacher, accused the Government of "failing in their most basic of tasks" by "relying on unqualified teachers to plug the gaps".
He said: "Unqualified teachers have no guaranteed training in safeguarding children, controlling a class or adapting teaching to respond to the strengths and needs of all pupils.
"But under the Tories, they're responsible for the education of hundreds of thousands of our children."
Mr Kane said the Government's decision to change the rules on employing unqualified teachers was "permanently threatening standards" in the classroom.
"There is nothing more important to a good education than excellent teaching.
"The Tories' failure on teacher recruitment is putting school standards at risk and it's our children who will pay for their mess."
A Department for Education spokesman said: "The number of teachers overall has risen by 3.5% since 2010 and the proportion of qualified teachers in schools remains high.
"Nine out of 10 schools are rated good or outstanding and we have record number of teachers in our classrooms - 95% of which hold qualified teacher status.
"The rest include some trainees working towards their professional qualifications as well as experts, such as leading scientists, sports people or musicians, who headteachers think can add value to individual lessons and enrich the learning experience for children."