A leading Birmingham independent school has lashed out at Labour's plans to force them to do more to support the state sector, including competing against them at sports.

King Edward's in Edgbaston was responding to comments from Shadow Education Secretary Tristram Hunt, who announced independent schools would be made to take on the state sector in regular matches and debates – if they want to keep tax breaks, worth hundreds of millions of pounds.

The contests are part of Labour's proposed "school partnership standard" which would be used to judge whether fee-paying institutions should qualify for business rates relief worth an estimated £700 million over a parliament.

Mr Hunt, MP for Stoke-on-Trent Central, said: "Over the last few years we have seen the limitations of asking private schools politely. So the next government will say to them 'Step up and play your part. Earn your keep. Because the time you could expect something for nothing is over'."

But John Claughton, Chief Master of King Edward's School, said: "We feel that what we are doing here is almost unique in the whole of the independent sector and it needs celebrating and stating as a response to the implied criticism of Tristram Hunt.

"We are very conscious of our civic and moral duty to provide education for the brightest and raise aspirations in the city."

The school has 850 pupils of whom 193 are an on assisted places scheme, reducing the fees parents pay. Of these, 70 are charged no fees at all and 99 pay less than 10 per cent of the fees.

And in future years, almost a third of new pupils will be on assisted places scheme. In September 2014 and September 2015, at least 40 pupils out of 125 will receive a fee discount.

The scheme is possible thanks largely to the generosity of former pupils – who raised £7.5 million to subsidise the assisted places scheme.

King Edward's claims to be "probably the most socially and ethnically diverse independent school in the country" thanks to the assisted places scheme. Six in ten of new pupils are Asian and one in five are Muslims.

It also runs an outreach scheme designed to encourage pupils from all backgrounds to consider applying to the school and works with 130 different junior schools.

Mr Claughton, in a paper setting out the school's work, said: "Greater diversity has enhanced our performance whilst enabling us to enact our historic purpose. We have not become the preserve of oligarchs because there aren't any round here. We have become more open to all than since 1979."

Some schools have responded angrily to Mr Hunt's plans.

The headmaster of his own former school has said Labour's plans to strip private schools of tax breaks worth hundreds of millions of pounds unless they do more to help the state sector could be deemed "offensive bigotry".

Mark Beard, head of the independent University College School (UCS) in Hampstead, north-west London, said the shadow cabinet minister should be considering "new, helpful initiatives" to raise standards in state schools instead of trying to "tastelessly quantify" the value of public benefit his former school generates each year. In a statement, Mr Beard said: "If the shadow education secretary were to visit his old school, what would he find?

"A diverse pupil population from all creeds and backgrounds, with £1 million per annum granted for fee assistance, the vast majority for 100 per cent bursaries.

"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 an offensive bigotry?"

Mr Hunt said that if Labour takes power at next year's general election, it will legislate to ensure schools only qualify for the "subsidy" if they are judged to be meeting the criteria, which also include providing teachers in specialist subjects and helping state pupils get into university.

He pointed to figures showing that just three per cent of private schools sponsor an academy, while five per cent loan teaching staff to state schools and a third share facilities.