Olympic medallist Phillips Idowu told today how he was forced to jump over the fence to get into an athletics track as a child because he could not afford the entrance fee.

Triple jumper Idowu, 29, from Hackney, warned that poor children with top sporting potential may never win medals for Britain because they cannot afford to train.

He used to dodge the £2 admission charge at Mile End stadium two or three times a week after school for several years, before he became good enough to get financial support.

His family could not pay the £2 ticket on top of his bus fare each session.

Last month in Beijing he held up a silver medal in front of cheering fans.

Idowu said it was "outrageous" that anyone under 18 had to pay to train at proper facilities.

Backing the Evening Standard campaign, he said: "It seems a small amount, but paying that and travel three times a week when you’re poor is a huge barrier and puts kids off. You only get funding once you’re recognised nationally as good, so the first few years of proving that [you are good] are a struggle if you aren’t well off. You need to use proper tracks to succeed. I can understand why adults have to pay to use them, but kids? It’s ridiculous, outrageous."

He said wider access to grass-root initiatives should be a legacy of the 2012 Games because it could tackle London’s gang-crime epidemic. "Give a kid a chance to run or take up some other sport properly and that’s a focus for their aggression. They start believing in themselves and see a life that’s not hanging around on the streets.

"I was never drawn into that stuff as I always knew I wanted to be a top athlete. I have no idea how I kept at it. It was really tough but once you start there’s a drive to win and my PE teachers at school were really encouraging."

Idowu said sports stars had a responsibility to inspire young people and mentoring schemes should be encouraged. "Seeing top high jumper Dalton Grant train at Mile End one day after school really pushed me on," he said. "I reminded him years later that I’d got him to autograph my homework diary."

He added: "The welcome back I’ve had from Beijing has been incredible. It will be an unbelievable, life-changing experience for British sportsmen and women who win in London. I’m determined to take the gold in 2012 and push on for another four years, so who knows who I can inspire in that time."

Meanwhile, Idowu is determined to overcome the disappointment of missing out on the Olympic triple jump title in Beijing, by winning gold in London in 2012.

The Hackney born and raised triple jumper fell short in his attempt to put a golden finish on an excellent season last Thursday, when he was narrowly beaten by Portugal’s Nelson Evora at the Bird’s Nest stadium.

"I didn’t come here for a silver medal, so I’m not going to be content with what I have got," said Idowu.

"It’s another four years but I will go on. I’m a winner - I want to clean up, sweep everything on the way to London. I have no choice but to carry on."

World indoor champion Idowu had been a clear favourite to take Olympic gold leading up to the competition, but despite jumping a season’s best 17.62m, he was forced to settle for silver, when Evora snatched the top prize with a fourth-round leap of 17.67m.

It was the first event this year that the 29-year-old had failed to win but he could console himself with the knowledge that he had been involved in a close-run competition.

This was the first Olympic final in which more than two people jumped 17.50m, with Leevan Sands, of the Bahamas, making it a three-way battle for the gold medal.

Idowu began the night in positive fashion, leaping to the front of the field with a clean first jump of 17.51m that appeared to justify his position at the top of the world rankings.

He was pushed back into the bronze position in the second round as Evora and Arnie David Giralt, from Cuba, both exceeded his opening mark, but Idowu responded with a third-round effort of 17.62m to restore his position at the head of the field.

Yet Evora’s fourth jump proved decisive. The Portugal athlete, who originally represented the Cape Verde Islands, produced an improvement of 33cm on his season’s best and left Idowu trailing by 5cm.

Idowu would have needed a jump equalling his all-time personal best of 17.68m to take the title and it proved too much for the Belgrave Harrier, who comes from the De Beauvoir estate in Hackney and who attended De Beauvoir Primary School, Tottenham Road, N1.

"It was way off from what I needed to do for gold," he said. "I came here with a plan, but didn’t do any of that. I jumped further than I have done this year, but it wasn’t enough.

"I felt like it was a failure - all year I have been jumping around 17.50m and taking off around 20cm behind the board so all I needed to do was what I have been doing all year, bang on the board and I would have had 20cm on the guys.

"Even if I had taken off 20cm behind the board I should have been jumping as far as the winner.

"There were a lot of people who came here to support me and as well as letting them down, I’ve let myself down too. I don’t like the colour silver, that’s not going to happen to me again."

Idowu added that he will now attempt to finish the season at the top of the world rankings as he begins to prepare for next year’s World Championships in Berlin.

"I want to finish my season ranked number one in the world," he said. "Next year I want to be so far ahead of everyone else in the world that even if I underperform by 50cm, they’ll still be 20cm behind.