The majority of classroom teachers think it is too difficult for schools to sack underperforming colleagues, new research in England has found.
Heads' leaders say the result of a survey of more than 2,100 teachers strengthens their calls for new procedures to make it easier to get rid of weak members of staff.
But a classroom union said the view expressed by teachers in the poll, commissioned by the Sutton Trust, was "regrettable".
The survey found that majorities of both school leaders - 73 per cent - and classroom teachers - 52 per cent - agreed there was "not enough freedom for schools to dismiss poorly performing teachers".
Last month, the Government announced a review of teaching standards, noting they did not "fit easily with the procedures for tackling underperforming teachers".
Just 21 per cent of all teachers think schools have enough freedom to sack incompetent colleagues, according to the National Foundation for Educational Research's survey of a weighted, representative sample of the profession.
But 57 per cent wanted to see greater freedoms, with very similar majorities in both the primary and secondary sectors.
NUT general secretary Christine Blower said: "It is regrettable that colleagues agree it is not easy enough to dismiss teachers.
"I wonder if the people that said yes to that question would change their minds if they found themselves being put through capability proceedings?"
Russell Hobby, general secretary of heads' union the NAHT, has called for the "capability" system to be streamlined so that it is possible to fire incompetent teachers within eight weeks. He said the survey added weight to his cause.
"In every profession I have worked in, the one thing that annoys people who are really working hard is seeing others getting away with doing a less than good job," he said.
Sir Peter Lampl, chairman of the Sutton Trust, which campaigns for greater social mobility through education, said: "I think the answer with underperforming teachers in general is not to fire them, it is to turn them around.
"I am a great believer in human nature and I think most people, given the right motivation and training, will do a good job."