Londoners shouldn't let excitement about a fortnight in 2012 detract attention from the longer-term challenge

As City Hall is only too aware, only around 1,000 days remain before the London Olympics to create the greatest show on earth. But is it simply about a fortnight in August 2012, or is there much more at stake? I'll be enjoying the Olympics and Paralympics as a sports fan but, like Lord Coe, I am more concerned in the longer term with the legacy of the games.

The games will transform London forever. They will create a major new city centre at the heart of the planned Thames Gateway metropolis; and they could transform attitudes to health, fitness and wellbeing by improving access to sports. This is a once in a generation chance to shape the future destiny of a city, the communities, neighbourhoods and its citizens. London taxpayers are contributing to the games and therefore should be driving this forward.

Let me touch on the two most important legacies: sports and the Olympic Park.

Sports legacy is a thorny issue. No Olympics has resulted in a greater uptake of sport by people living in the host city beyond the first few weeks after the games. This is akin to "the Wimbledon effect", a reference to those who spurred on by the tennis tournament take out their rackets in June only to put them away at the end of July. Kate Hoey has been charged by the mayor with the not so simple task of developing a sports legacy. All want a concerted effort to improve access to sport for those with disabilities, those who can't afford it and those who for cultural, religious or psychological reasons can't find appropriate sports sessions eg single-gender swimming.

London has three years to find innovative ways of promoting sport and paying for access to it. Communities, government and business need to work together. It benefits us all – individuals feel better and live longer, businesses have a healthier workforce and the state has a reduced public health bill. The Olympic Park combined with neighbouring Stratford City will create a Thames Gateway capital. Londoners can still shape this new city. Baroness Ford, the new Olympic Park Legacy Company (OPLC) chair raised concerns recently that the park should have more affordable and family housing or risked becoming a second Canary Wharf.

Residents living in the park's vicinity have to benefit from it for the park to rejuvenate one of the poorest areas of the capital. Engagement with local communities by the OPLC is to be applauded but residents need to take up that opportunity or louder voices might prevail. There are many questions over the park's future use including that of the stadium. The current orthodoxy is that it will be downsized from an 80,000 to a 28,000 athletics venue; other ideas include a cricket stadium or an England World Cup 2018 bid venue. Olympic stadiums – as with the Millennium Dome – always risk being a one-minute wonder. It has taken almost a decade for the dome to become the successful 02 Arena venue.

The Olympics will no doubt demonstrate that Britain can deliver a world event. However, for the legacy to be a success, Londoners should engage with the Olympic authorities now, because by 2012 it will be too late to influence the shape of this city for decades to come.

Alexander Goldberg is on the Jewish Committee for the London Games and writes here in a personal capacity.