Claims that 90 per cent of pupils do at least two hours of high quality PE every week are "hard to believe", according to a manager overseeing sport in more than 30 schools.
The Government has claimed a victory with its annual school sport survey, which shows record numbers of children hitting the target.
Ministers said they had smashed their goal of 85 per cent of pupils doing the two hours of high quality PE and school sport a week - up from just 25 per cent in 2002.
But one partnership development manager, who is responsible for co- ordinating PE provision in more than 30 primary and secondary schools in the south of England, said: "I seriously doubt the figures. I have spoken to other managers and none accept they are correct.
"Schools and development managers feel under pressure to fudge the figures because they don't want to be criticised.
"Ultimately we are letting down the pupils that we came into these jobs to help."
He complained of red tape involved in getting experienced and qualified outside sports coaches into school, and said that some primaries reduced PE with Year 6 pupils after Christmas as they prepared them for key stage 2 tests.
Margaret Talbot, chief executive of the Association for Physical Education, said the crowded curriculum in the run up to GCSEs was a major problem for schools.
The survey found a sharp drop-off in secondary schools hitting the two- hour target - down to 83 per cent of pupils, compared to 96 per cent in primaries.
But the figures were particularly bad for pupils in Years 10 and 11, with participation rates at 71 per cent and 66 per cent.
"The key stage 4 curriculum is very crowded, which drives down the amount of time dedicated to PE," said Professor Talbot.
"There is a whole range of things that schools are expected to do, combined with concerns about exam performance.
"It can be difficult for schools, but we don't think two hours a week is too much to ask for."
That target can include PE and school sport done both inside and outside of the timetable. But the figures show that the majority of pupils get their two hours through the school curriculum.
Professor Talbot said the trend of the survey, run over five years, showed considerable improvements and should be celebrated. But she called for more investment to ensure that PE is sufficiently high quality.
The sport survey is carried out by an independent research company on behalf of the Department for Children, Schools and Families.
Researchers visited 45 of the 450 school sport partnerships in England and said it was confident that its results were robust.
Ed Balls, the schools secretary, said: "Ignore the half-pint full critics who carp nothing has changed. School sport was a national embarrassment a decade ago.
"Sport had all but withered and died in many schools; thousands of playing fields had been sold off, there was negligible investment and an ingrained anti-competitive culture."
The figures show that competitive sport has increased in the past five years, with 66 per cent of pupils taking part in intra-school competitions this year, up from 58 per cent in 2007.
SPORTS AWARDS WERE MADE EASIER
The latest figures follow criticism of the Government for watering down awards given to schools where high numbers of pupils take part in PE and sport.
As revealed in The TES, changes have been made to the Activemark and Sportsmark awards, which are given to primaries and secondaries respectively. This has led to a doubling in the number of primaries and a quadrupling in the number of secondaries holding the awards in just one year.
The criteria have been made easier so that any school where 90 per cent of pupils do two hours of high quality PE and school sport a week is now eligible.
PE teachers said the move was designed to improve figures in the run-up to the 2012 Olympics.
The Department for Children, Schools and Families said the changes had been made to encourage more schools to increase their provision.