The report by the think tank Sportnation, called A Sporting Chance, claims that those born later in the selection year are much less likely than their elders to be chosen for elite teams and squads and therefore miss out on coaching and development opportunities. Among those it claimed might have been lost to British sport as a result is the Liverpool and England footballer Steven Gerrard.

The Sportnation panel, chaired by Steve Cram, the former world record holder for the 1500m and mile, and made up of senior figures in business and academia as well as sport - including the former Scotland rugby captain Gavin Hastings - has called for a radical rethink of the selection of youngsters for teams and squads in the light of research conducted by Loughborough University.

Its report identifies a huge bias towards older children in the selection year, usually the school year. An estimated 30,000 talented youngsters may have been left on the sidelines by the relative age effect.

The study found that 67 per cent of those in the Football Association's school scheme are born between September and November, compared with only two per cent between June and August, and only 8 per cent of finalists in the under-15 events at the English Schools' Athletics Championships were born between June and August.

The research highlights how great the physical difference can be for children born at different ends of the academic year. It shows that a 14-year-old boy born in September will be on average 7cm taller and 5.7kg heavier than a boy in the same class born in August, yet they compete for a place in the same team.

Given this, the report says, it is hardly surprising that most professional footballers and cricketers in Britain are born between September and December.

Gerrard, born in May and a late developer, attributes his failure to get into the FA school at Lilleshall and the England Under-16s to his early small stature. Michael Owen, born almost six months earlier, made both squads easily.

"I think Sportnation has touched on a really important issue," said Gerrard. "It cannot be fair that many of the youngest kids in the school year are left on the sidelines. I was lucky because my parents and the coaches at Liverpool kept complete faith with me until I developed more physically.

"I know many youngsters are not so lucky and anything that can be done to put this right has to be a good thing for sport in this country."

Cram said: "My former rivals, Sebastian Coe and Steve Ovett, were born around the same time as me, in October. And two school mates - one was captain of the football team, the other the rugby team - were also born at the same time."