It seems likely that we will have to prove that we also provide a 'perceived public benefit' and we will have to demonstrate this, through bursaries and partnership schemes

Gill Lumsdon, chair of IAPS

At present, charitable status provides tax benefits for private schools - but Mrs Lumsdon warned that this position could be under review.

And to protect the future charitable status of private schools, she stressed the need for schools to show that they could provide benefits to the wider community, such as sharing facilities with the state sector.

The speech also raised the prospect that conditions could be attached to the granting of charitable status which could restrict independence for private schools.

'Hidden agenda'

Mrs Lumsdon, headteacher at Kensington Preparatory School in London, warned that reviews of the charity system by the Charity Commissioners and the government could challenge the granting of charitable status to schools.

"There is a strong likelihood that schools may no longer be able to rely on an automatic acceptance that education is intrinsically a charitable activity," she said.

"It seems likely that we will have to prove that we also provide a "perceived public benefit" and we will have to demonstrate this, through bursaries and partnership schemes.

"It does concern me that there might be a hidden agenda behind this activity. I certainly hope I am wrong, but is there a chance that the granting of charitable status might also depend on further accountability, resulting in an undermining of our independence?"

The association represents 500 independent primary schools, teaching about 130,000 pupils.