Ofsted announces plan for lightning-bolt visits
The new system, to be launched in 2009 if a pilot next year is successful, aims to reduce schools' ability to stage-manage inspectors' visits.
At present, most schools deemed good or better receive visits every three years, with 48 hours' notice.
Christine Gilbert, chief inspector of schools, said Ofsted also hoped to move towards a more "tailored approach" to inspection, varying the intervals between visits.
Headteachers' unions have reacted angrily to the proposals, saying they would lead to heads keeping watch for inspectors "at the school gate".
Ms Gilbert also said she hopes to make greater use of "local knowledge" - from parents, pupils, and local authorities - to flag up problem schools in need of a lightning-bolt visit.
Last year, Ofsted launched a hotline so that pupils and parents could call in with their concerns.
Ms Gilbert told the children, schools and families select committee this week: "We are considering representations from parents and pupils that inspections should take place without any prior notice.
"We will look at the practicalities of no-notice inspection as part of our planning for the new school inspection framework."
The plans are also designed to counter concerns that the "light touch" inspections carried out in around 30 per cent of schools might fail to spot problems.
But John Dunford, general secretary of the Association of School and College Leaders, said cutting out the 48-hour notice period was wrong and that Ofsted should consider ditching mandatory inspections altogether.
He said: "No-notice inspections would be more punitive and create increased stress as heads keep a constant watch on the school gate for the arrival of the inspectors."
The hardline proposals from Ofsted come as a primary head in Norfolk has spoken out about the confused messages her school has received from the schools watchdog and the Government.
St Edmund's Community Primary in King's Lynn was praised recently by inspectors for its work with children from deprived families, receiving a good rating overall and an outstanding rating for its pastoral care, support and guidance. But the Department for Children, Schools and Families has also contacted the local authority, describing it as a "cause for concern" because fewer than 65 per cent of its pupils reached level 4 in key stage 2 English and maths for three consecutive years.
The criticism comes despite the school being ranked fourth out of almost 90 schools in west Norfolk for its value-added results at KS2. Rebecca Elliott, its headteacher, said: "We are not struggling at all in terms of value-added. Some of our children make tremendous progress.
"We have strong pastoral care and have built good relationships with parents to help engage them with what we're doing."
Ofsted triggered suicide, page 6
My Whitehall nightmare, page 22.