The advice is expected to be given in a new government information pack to be published this week, aimed at preventing schoolchildren misusing computers.

Teachers are advised to carry out spotchecks on pupils

Similar checks by employers have already cost a number of workers their jobs, as companies have cracked down on staff misusing computer equipment.

Education Secretary David Blunkett is expected to suggest that children found using computers to gain access to "inappropriate" material could be denied use of the Internet, either permanently or for a period.

The advice comes as children's access to the Internet, both at home and at school, is expanding fast.

The government is committed to a £1bn investment which will link every school to the Internet by 2002.

12,000 primary schools have Internet access

Already, 90% of secondary schools are online, and over the past year the number of primary schools with access has increased from 3,000 to 12,000.

The advice also guides schools as to the protection systems already available to prevent pupils misusing computers, or from being contacted by unwanted persons.

Some enable schools to establish "walled garden" networks on their computer systems, which limit pupils' access to suitable sites.

Other systems set up "firewalls" which prevent pupils themselves being contacted by e-mail from outside the school.

David Blunkett hopes every school will be online by 2002

The government has pledged that by 2002, every child will have their own e-mail address.

The pack will also contain a poster aimed at young pupils using a Disney cartoon character to drum home messages about Internet safety - including protection of their e-mail address.

The pack also advises parents to site home computers where they will be able to monitor the use that children make of them, rather than in their bedrooms.

And it says parents should join their children in "surfing" the Internet, so they can guide them to suitable websites.

One teacher who has already drawn attention to the dangers of the Internet said on Sunday that he was now most concerned about children's use of chatlines.

Mike Moore, head of IT at Little Hulton Community School, Salford, and an executive member of the Association of Teachers and Lecturers, said it was relatively easy for schools to control children's access to text and images on the Internet.

"But I am very concerned at children laying themselves open to abuse by divulging personal details to total strangers via chatlines which can also be accessed on the Internet," he said.

"I don't see how we can monitor this," he said.

"If children are going to get involved in this kind of immediate response service, it makes it much more difficult - if not impossible - to monitor.