Hampstead and Highgate’s private school leaders have united against Labour’s plans to revoke tax breaks for independent schools if they don’t support the state sector – after the head of the shadow education secretary’s old school accused the MP of “offensive bigotry”.

Former University College School (UCS) pupil Tristram Hunt MP announced on Tuesday that, if elected, Labour would strip private schools of up to £700million of business rate relief over the next Parliament unless they agree to do more to support the state sector.

The suggestion that independent schools do not do enough to earn their tax relief prompted a furious backlash from UCS headteacher Mark Beard, who called Mr Hunt’s remarks “tasteless”. His views have been echoed by many private school leaders locally.

Mr Beard said independent schools benefit the public far more than the value of any tax relief accrued from being registered as a charity.

In a statement, he said: “If Mr Hunt wanted to tastelessly quantify the value of public benefit that UCS generates each year, then he would find that it far outstrips the value of tax relief that UCS receives through its charitable status. And UCS is not alone in this regard.”

He added: “Rather than rely on independent schools to solve the issues for the 93 per cent of children who are educated in the state sector, isn’t it time for Labour to come up with some new, helpful initiatives rather than espousing what some might deem as offensive bigotry?”

Under the policy, private schools would sign up to a “schools partnership standard”.

It would require them to deliver specialist knowledge to state schools, help disadvantaged pupils gain places at top class universities, and to run joint extra-curricular activities with the state sector.

Mr Hunt said he wanted to break down the “Berlin Wall” dividing the private and state sector, and that independent schools are not doing enough to earn tax relief.

He pointed to figures which reveal that only 3 per cent of private schools sponsor an academy, 5 pc loan teaching staff to state schools, and a third share facilities.

Mother-of-four Tania Levenfiche, a UCS parent for 16 years, said: “He has benefited from an amazing education at one of the top independent schools in London and now is trying to knock the system down – I think it’s shocking.”

Local independent heads said Mr Hunt has downplayed the work private schools already do to support the state sector.

Helen Pike, headteacher of South Hampstead High School, said: “Let’s not make this about a transaction. This isn’t about the funding, this is about mutually beneficial relationships.”

Jonathan Taylor, headteacher of North Bridge House School in Hampstead, said: “Mr Hunt is right to suggest private and state schools should enjoy relationships of respectful, advantageous interaction.”

But he added: “Good schools will do these things regardless of the tax break issue. I am sure Mr Hunt would want to celebrate those schools who very much do contribute to their local communities.”

While broadly agreeing with the policy, Highgate School headteacher Adam Pettitt said: “I wonder if policy-makers should not re-angle their thinking to promote the importance we – society and individuals – place on our education and on opportunity wherever we find it.”

A spokesman for the Independent Schools Council (ISC) said: “We completely support Mark [Beard]’s remarks.” ISC chairman Barnaby Lenon added: “Clawing back business rate relief on independent schools seems a very ineffective tool to improve social mobility in any meaningful way.”