Almost half of head teachers have cut special needs support this year in a major threat to Labour's landmark education reforms, polling suggests.
A survey of 330 school leaders found 43 per cent said they had cut support to pupils with special educational needs and disabilities (Send) since last year.
In addition, 81 per cent said they expect to make future cuts across the board, with the majority saying teaching assistant numbers would be reduced.
The report, from the Sutton Trust, comes just two months after Labour published plans to shift more responsibility for Send pupils onto mainstream schools.
Under the plans, it is thought more of these pupils will be given places in everyday schools, rather than in specialist provision.
Today's report said there is an 'urgent need for action' on staffing capacity 'if mainstream schools are to educate more pupils with Send'.
It added: 'There remains considerable uncertainty about how the huge Send reforms will be paid for.'
Pepe Di'Iasio, General Secretary of the ASCL heads' union, added: 'This research shows the contradiction between the Government's aspirations for the education system and the amount of money that it is prepared to provide.
Almost half of head teachers have cut special needs support this year in a major threat to Labour's landmark education reforms, polling suggests (pictured: Education Secretary Bridget Phillipson)
'Many schools are having to cut resourcing for Send support at exactly the time the Government has launched a programme of major reforms which involve far more expectations on mainstream schools.
'Although the Government has made some additional funding available, this is unlikely to be sufficient.'
Under Labour's plans, unveiled by Education Secretary Bridget Phillipson in a White Paper in February, all but the most profound Send cases will be dealt with by mainstream schools.
The new system is designed to reduce the rising cost for councils of providing expensive support for pupils with less severe needs.
As part of a funding package to deliver it, the Government will provide an 'inclusion grant' of £1.6 billion over three years for schools.
However, teaching unions have said this only equates to one extra part-time teaching assistant for the average primary school, and two teaching assistants for the average secondary.
The poll, carried out by the National Foundation for Educational Research (NFER) for the Sutton Trust, also found 71 per cent of heads have reported cutting teaching assistants in the last year.
Meanwhile, 49 per cent have cut support staff and 30 per cent have cut teaching staff.
Daniel Kebede, general secretary of the National Education Union, said: 'This is the uncomfortable reality that the Government simply will not face up to.
'Schools are running on empty and are having to make cuts to essentials simply to survive.
'It is impossible for schools to meet the Government's ambitions on Send support.'
The Department for Education has been contacted for comment.