Ministers have failed to deliver on a key Olympic pledge.

They are accused of betraying a generation as figures show schools are missing a basic target of providing two hours of activity for children a week.

MPs accused the Government of "disgraceful" failure over promises linked to the London Games. It comes as the Standard campaigns to secure a proper sporting legacy for the capital in the run-up to 2012.

The figures also cast doubt on the Government's aim to get children doing five hours sport a week, both in and out of school, as part of new "Olympic era". Culture Secretary Andy Burnham unveiled the plan last week as part of a £32million drive to make "coaching and competition" available to all children by 2012.

Figures obtained by the Standard show that half of London boroughs, 15, are not meeting the target of getting 85 per cent of pupils active for two hours a week to reverse a long-term decline in school sport.

Olympic host boroughs are among the worst performers, with just 78 per cent of schoolchildren in Greenwich doing two hours a week.

Tower Hamlets and Hackney also failed to meet the minimum standard despite helping to host the Games.

Shadow schools minister Nick Gibb said: "It is a disgrace that just a few years before 2012, ministers are so far away from their target to get pupils into sport. We must do more to ensure that all pupils get the chance to participate in sports."

Liberal Democrat shadow culture secretary Don Foster said: "If we're serious-about our improving children's health then two hours of sport should be the absolute minimum. All the Government needs to do is write that into the curriculum."

On average, London hit the 85 per cent target but this was one per cent below the national average, which shows a gradual trend towards every pupil playing two hours of sport by

2012. One of the best performers was the main 2012 host borough of Newham. It was joint top of the London table with Richmond upon Thames, after making sure 91 per cent were getting two hours of sport a week while at school.

But the figures also show the Government's campaign to promote competitive sport after decades of neglect has failed to take off in the Olympics boroughs.

Just 27 per cent of pupils in the five host boroughs were involved in interschool competition during the last academic year on average, compared to the London and national averages of 32 and 35 per cent respectively.

London schools also score lowest nationwide for the number of pupils involved in sports volunteering. Just 10 per cent of London children have become volunteers such as marshals at sports events compared to a national average of 12 per cent.

There is growing concern over activity levels for 14-16 year olds, with nationwide figures showing participation rates falling to 63 per cent in the final year of secondary school.

Figures on school sport for 2006-7 were compiled for the Government by teachernet.gov.uk and are based on questionnaires sent to PE teachers at 22,000 schools. Data from the last school year will be published next month.

A spokesman for the Department for Children, Schools and Families said: "London now has some of the fastest increasing youth sport provision in the country and we expect participation rates to rise again when this year's survey is published - but there is more to do in the run up to 2012.

"London has some tough areas and boroughs like Greenwich are using innovative approaches to engage young people in positive activities in school.

"We're investing unprecedented amounts in rebuilding and revamping every secondary school, including top notch sports facilities, in London through the Building Schools for the Future programme - including an academy on the Olympic site."

The Evening Standard's charter to deliver an Olympic legacy

• Create sporting inspiration and facilities "that last for the generation to come"

• Secure access to top-class sporting facilities for all

• Ringfence money to secure Olympic legacy and ensure millions more participate in sport

• No more sell-offs of school or council sports facilities

• Establish a system of "Olympic Champions" with top athletes going into schools to inspire children, teachers and parents