The majority of classroom teachers think it is too difficult for schools to sack underperforming colleagues, new research 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".
It also suggests that teachers opposing an expected reform of the system, which some schools say is too cumbersome, could be outnumbered by more than two to one.
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?"
She said teachers had a difficult job, were not given enough support and on-the-job training, and her union would resist attempts to make sackings easier.
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.
"Some of them you can't do anything with and have got to fire them. But I am a great believer in human nature and I think most people, given the right motivation and training, will do a good job."
The survey also asked teachers to prioritise where schools should spend any extra money they got through the pupil premium, which is targeted at the disadvantaged.
Smaller class sizes got by far the biggest support (backed by 44 per cent), followed by extra teachers (16 per cent) and extra support staff (14 per cent).
The poll found that 52 per cent of all teachers thought schools should be able to offer pound;10,000 pay increases above normal salaries to recruit and retain effective teachers to improve the education of disadvantaged pupils.
Schools that have the money can already do this, but only for fixed periods of up to three years which can only be extended under "exceptional circumstances" where the money is being used for staff retention.
Secondary leaders were evenly split on the idea, with 39 per cent both for and against, leading the NFER to speculate they were concerned about a lack of funding.
INSPIRATION FROM OBAMA
pound;125m BOOST FOR DISADVANTAGED
The Sutton Trust is to lead a pound;125 million programme aimed at boosting the achievement of disadvantaged pupils in under-performing schools, inspired by President Obama.
The Government-funded education endowment fund will hand out grants to "innovative and bold" proposals from schools, teachers, local authorities and charities.
It is based on President Obama's Race to the Top, which uses a similar competition for grants to encourage school reform.
Sir Peter Lampl, chair of the Sutton Trust, said the fund represented the culmination of his charity's work. Impetus Trust, another charity, will be a partner in the project.
Original headline: Make firing easier: teachers' verdict on underperformers