Ministers are believed to have taken the decision to preserve swimming after warnings that more children will drown unless a legal requirement remains in force.
New curriculum guidance to be announced this week is expected to allow schools to decide for themselves which other activities they teach during PE lessons, though they will be advised to continue with at least some games and athletics.
The decision is in sharp contrast to that taken by Peter Hain, the Welsh education minister, last week. He announced that running, throwing and jumping as well as swimming would be compulsory to protect children against heart disease.
Earlier this year, David Blunkett, the Education Secretary, decided that, from September, legal requirements for the primary curriculum would be reduced so that schools could spend more time on literacy and numeracy. Detailed programmes, he said, would be compulsory only in maths, science and English. In the remaining six subjects, including PE, teachers would be free to choose what they taught.
Critics accused him of narrowing the curriculum and threatening the future of subjects such as music, art and PE. He pointed out that schools would still be legally obliged to teach all these subjects. At present, swimming is one of six skills taught in PE. The others are games, gym, dance, athletics and outdoor and adventure activities.
Ministers decided to make an exception of swimming after a campaign by the Amateur Swimming Association and the English Schools Swimming Association who argued that many schools were facing real difficulties in organising swimming lessons in times of financial hardship: if the law were changed, they might drop the subject altogether. Swimming's supporters said that the sport was a special case because it saved lives as well as keeping children fit.
John Lawton, director of education at the Amateur Swimming Association, said: "Children from disadvantaged backgrounds and some ethnic minorities do not learn to swim outside school. If children don't swim at school we shall end up with a generation which has never had the opportunity to learn."
Ministers, who have come under pressure from well-known musicians and artists, are anxious to emphasise that music, art, history, geography and technology must remain on the timetable: teachers will be able to choose topics from the existing curriculum. The approach is different from the one adopted by Welsh ministers and civil servants who have decided that some skills and topics are too important to be left to chance. True to Welsh choral traditions, singing a variety of songs with control of breathing, dynamics and pitch will remain compulsory for five to seven- year-olds. In history, Celtic Society must still be taught to juniors but teachers may opt for Tudor or Stuart Wales.