London children get significantly less time to learn to swim than their classmates in Wales, according to a TES survey of swimming tuition in primary schools.
The capital's pupils can expect just two-thirds of the time given to those at Welsh primaries. But it is pupils in the Midlands who are least likely to achieve the required skills.
The survey shows how some regions offer far more swimming opportunities than others and reveals wide variation in skills across the country.
Welsh pupils get the best chance: on average, primary children in Wales get the equivalent of one hour's tuition every week for a year. Pupils in South-west England and in the South-east outside London also get more swimming time than the average for pupils in England.
By contrast, pupils in the capital can expect the equivalent of only 40 minutes per week. Those in the North also get below average pool time.
Lynn Watkins, head of Shiney Row primary in Sunderland, said: "The budget has prevented (swimming lessons) this year. It was a decision made by the governing body, led by the acting head, that there were other priorities."
An average of 88 per cent of pupils in Wales met each national curriculum requirement compared to just 71 per cent in London. Pupils in the Midlands were the least successful, however, with only 67 per cent reaching the required standards.
Schools said lack of cash had forced them to press parents into paying the cost of transport and pool hire. About half of schools asked for some contribution from parents. The average charge was pound;2.30.
Not all schools can rely on parents. Woodland Park primary in Devon reported "great difficulty" getting contributions for swimming lessons from parents, although it is in a middle-class area.
Schools also blamed poor facilities, high costs and an overcrowded timetable for the fact that so many pupils are failing to master basic strokes and survival skills.
Pool closures and a lack of local facilities have led to many pupils spending as long travelling to and from their "local" pool as they did swimming. The average round trip is now 30 minutes.
Kevin Buckley, head of Cliftonville primary school in Margate, Kent, said:
"There is an appalling lack of facilities locally, despite it being a coastal town. This makes it impossible to satisfy the legal requirements."
Even schools with their own pools are experiencing difficulties, with some closing them because of maintenance costs.
Julie Branche, head of Farcet Church of England primary in north Cambridgeshire, said: "We have an on-site pool. It is a total red herring - expensive, ineffectual and a total health and safety nightmare.
Community-built 30 years ago, it's a local 'hot spot' should I dare to close it."
Despite the difficulties, schools recognised the importance of swimming.
Jaqui Symes, head of Victoria Road primary school in Northwich, Cheshire, said: "Swimming lessons are essential in an area surrounded by water. Most of our children would not learn to swim if this was not done through school."
But not all schools accept that the national swimming targets make sense.
Peter Stonier, head of Newstead primary in Nottinghamshire, said: "The 25m requirement is a nonsense. It's just far enough to get yourself drowned."
Mavis Fox, president of the English School Swimming Association and a retired primary head, said: "I am disappointed things haven't improved despite a lot of people working very hard," she said.
In her own school it had taken one and a half hours out of the day to provide a 30-minute swimming lesson, she said. Cost and time pressures also meant many schools stopped lessons once children reached national standards.
Additional research by Richard Reynolds