Music stars of the future are being thwarted by a shortage of instruments and unsuitable classrooms, inspectors have said.

Improvements in teaching during the past year have been undermined by poor facilities, according to the Office for Standards in Education.

One in four secondary schools has inadequate music resources a situation Ofsted described as “unacceptable”.

Its verdict came as it emerged that David Miliband, schools minister, and Estelle Morris, the former education secretary and now arts minister, are drawing up a music manifesto to boost participation in schools.

Ofsted’s findings are based on routine school inspections during 2002-3.

It says that the lack of appropriate instruments and other equipment is having a negative impact on pupils’ work, particularly for 11 to 14-year-olds.

Sixth-formers are also badly hit, with one in three lessons taking place in an unsuitable classroom, a significantly higher proportion than in any other subject.

Despite these handicaps, good progress has been made in 52 per cent of secondaries since they were last inspected. Overall provision has improved in five out of six.

David Bell, the chief inspector of schools, described the improvements in teaching as good news for budding young musicians. But he said: “More must be done to help the Will Youngs of the future.”

Ministers will find it easier to up-grade music resources in primary schools to an acceptable standard, inspectors found. Only 6 per cent were judged to have unsatisfactory resources, although one in 10 schools had an unsatisfactory curriculum for seven to 11 year-olds Mr Bell warned earlier this month that primary schools were in danger of developing a two-tier curriculum with literacy, numeracy and science promoted at the expense of other subjects such as music.

Campaigners such as percussionist Evelyn Glennie and cellist Julian Lloyd Webber argue that music is being marginalised at school and this risks the future of classical music in the UK.

They have joined forces with pop stars such as Dido to persuade ministers to act.

The music manifesto will be launched this summer and will cover music education from early years to adults. It is expected to include a “statutory entitlement” to “a sound foundation in general musicianship”.

Ministers hope campaigners will formally back the proposals which include improved training for teachers and the use of professional musicians in schools.

The manifesto will stress the importance of young people having clear pathways through which they can achieve their musical ambitions.

It will also promise instrumental and vocal tuition in primary schools at a free or reduced rate.

Colin Brackley-Jones, chief executive of the Federation of Music Services, said: “This is a step forward. For the first time ministers are listening to what we are saying about school music.

“Now they need to take the next step and ensure schools have the money to buy instruments and other equipment.”

Labour promised in its 2001 election manifesto to “Ensure primary schools offer more chance to learn ... music” and “Provide primary pupils with wider opportunities to learn ... musical instruments”.

The Government’s own research suggests that only 8 per cent of primary pupils learn an instrument at school, while a survey for the National Union of Teachers found that primaries spend an average of 45 minutes each week on music, less than any other subject.

Mr Miliband, whose wife Louise is a professional cellist, said: “Every child should experience the power of music as a source of educational enrichment and enjoyment. We want to extend musical opportunities in primary and secondary education.”

He said that the 200-plus performing arts colleges, and the new specialism in music gave “the opportunity to create real centres of excellence”.

Matt Buck’s week 31