The 2012 London Olympics will fail to deliver any lasting sporting legacy for most young Britons because of six years of failed government policy and "missed opportunity", the chairman of the British Olympic Association says today.

In an outspoken attack, Lord Moynihan, who will manage the British team for next summer's Games, said that since the UK won the 2012 bid in 2005 politicians have failed to honour pledges to drive through a national, sporting revolution at school and grassroots levels.

In terms that will infuriate ministers past and present, Moynihan – who won an Olympic silver medal as a rowing cox – told the Observer that barring a last minute "step change" in policy to build better links between schools, local sports clubs and volunteers, the Games would spur precious little improvement.

"At the moment I don't see the policies being put in place that will build on the inspiration of the Games for young people and that will change their lives for a lasting sports legacy," he said. Pledges by the Labour government to deliver an average of five hours' sport a week in schools had not been met, and now further cuts were inevitable to local authority budgets thanks to the coalition's belt-tightening and refusal to ring-fence sports funding.

"There are too many schools still on two hours or less of sport a week, with no links to the local communities and clubs and volunteers, and that is a missed opportunity in the last six years. Politicians of all parties have the responsibility for setting policy and we have not seen that vision delivered," he argued.

Moynihan, a former Tory sports minister, said it was "unacceptable" that 50% of British medal winners came from private schools, when the independent sector accounted for only 7% of the total number of pupils. The reason was a failed system that did not give opportunities or nurture talent among state-educated pupils by building a ladder of progression from schools to clubs. "We have got tens of thousands of really gifted, talented young sports stars whose talent is never identified. There is no ladder for them to climb and there is no structure for them to get to the top of," he said.

The Olympics would be "hugely successful" in three respects, he said: the regeneration of east London, the organisation of the Games and the performance of the British team. But his bitter disappointment at successive governments' lack of vision over six years since winning the bid was evident.

The promise to deliver a permanent sporting legacy at grassroots level was at the heart of the UK's 2005 bid for the 2012 Olympics and was widely thought to have tilted the voting in London's favour. In 2006 Sebastian Coe, who spearheaded the bid and is now the chairman of London 2012, said: "Winning the Olympic Games and Paralympic Games represents the single biggest opportunity in our lifetime to transform sport and participation in sport in the UK forever.

"We have a unique opportunity that we must not squander to increase participation in sport, at community and grass roots levels as well as elite levels; from the school playground to the winner's podium."

The then prime minister, Tony Blair, attributed the success of the London bid to the fact that it made "a statement about sport and its importance in the development of young people for the future, in their health, in their fitness, in terms of their responsibilities as citizens".

Moynihan maintained that culture secretary Jeremy Hunt's plan for a national "school games" in the run-up to the Olympics would be good for paralympic sport but inadequate overall, because less than half of state schools had signed up. "There should be a universal policy. There should be no school that isn't engaged in the school sport network for the government's flagship project. Every primary and every secondary school should be involved in that."

When he became education secretary in May 2010, one of Michael Gove's first acts was to slash funding for sports in school and end all ring-fenced funding. After an outcry Gove restored some money but still refused to insist that headteachers spent it on sport.

Many organisations such as the Youth Sport Trust had done very good work, said Moynihan, but school sport remained a "patchwork".

Gove's desire to move away from micro-managed, centrally developed policy was correct, Moynihan argued. But he insisted that in the case of sport it could never work unless the money was earmarked for that purpose. "The problem is that if they [heads] have total discretion over the way they spend it, the same heads who undertook good practice in the past will continue and those who did not put a priority on sport will continue not to do so. If you make it mandatory to spend on sports provision, then the onus is on the school heads to engage with local clubs," he said.