Supply teachers should get the same working rights as council-employed school staff, a teachers' union has told the Government.
The Association of Teachers and Lecturers said proposed new laws on agency workers should be radically altered before they become law.
There are 14,000 supply teachers working in the UK but only those employed directly by local authorities are entitled to the same pay and conditions - including the chance to join the Teachers' Pension Scheme - as most state school teachers. Many agency workers are paid less pro-rata than teachers in full-time positions.
The Temporary Agency Workers Directive is designed to give those people "equal treatment" with basic working and employment conditions. But the ATL says the legislation does not go far enough. The union wants agency supply teachers to be allowed a teachers' pension, holiday and sick pay, and to havemore opportunity for professional development.
Martin Freedman, ATL's head of pay, conditions and pensions, said: "All UK teachers should get the same pay and conditions for the work they do, regardless of whether they are supply or permanent staff. If they are qualified to teach our children, then supply staff should be eligible to the same treatment.
"Schools would be in difficulties if we did not have a pool of professionally trained supply teachers able to step in and take classes when staff are sick, on maternity leave or training.
"While we are pleased that the Temporary Agency Workers Directive will become law, we are disappointed that the European Union directive has not gone far enough and the Government, Confederation of British Industry and Trades Union Congress have all declined to call for temporary workers to have access to pensions and sick pay."
The consultation on the legislation ends today.