Education authorities have been e-mailed the latest official guidance on vetting staff - detailing the policy U-turn forced on the government by the delays in background checks.

It tells them that people who are new to the school system or have had a career break can begin work, subject to the discretion of the head teacher.

The proviso is that they have been checked against List 99 - the Department for Education's database of about 2,500 people deemed unsuitable to work with children.

The department is taking back the List 99 checking from the Criminal Records Bureau (CRB), whose failure to process applications for checks quickly enough has led to thousands of schoolchildren missing the first days of term.

Online checks

To speed things up, the department is reinstating the secure online method of checking List 99 which the bigger employers of education staff had before the CRB began work this March.

U-turn: Estelle Morris

Employers without access to that system are told to nominate someone to e-mail in names for checking, in batches of not more than 100 at a time.

"It is crucial that care is taken to ensure that the information, including spelling of names, is accurate," the guidance says.

"If information is not accurate we could fail to identify a match with an entry on the List."

The department says it will aim to check and return lists within 48 hours.

Trainees

The checking process applies also to volunteer workers - with an appeal to prioritise those "essential to the smooth running of schools" - and to students starting teacher training courses.

In the past, trainee teachers often were not checked until they qualified and took up jobs in schools - this has been one of the factors contributing to the backlog of full checks on people's police records, known as "disclosures".

The department says urgent work will continue with the CRB "to ensure that all outstanding full disclosure checks are completed as soon as possible".

Further guidance to employers is promised for next week "on prioritising new applications for CRB checks".

It adds: "The department apologises for the disruption that has been caused, and will be writing direct to all head teachers."

'The buck stops here'

The new guidance - issued after schools had finished work for the day - is likely to satisfy the National Association of Head Teachers.

The union had complained that Wednesday's policy reversal by the Education Secretary, Estelle Morris, lacked detail.

Ms Morris said she had decided to give head teachers discretionary power to use unvetted staff, after finding out the criminal checks would not be completed for weeks.

The full checks still have to be done, but people can start work provided they have received the all-clear from the List 99 check.

Ms Morris told BBC News she wanted to thank head teachers for taking on the responsibility for making the decision on who to allow to work in their schools.

She stressed: "It's not me saying, 'Nothing to do with me, guv' - whatever decision they take I will back them to the hilt on that."

Loophole

At least one education authority - Dorset - had also said it wanted clearer guidance before letting unvetted staff into classrooms.

But others had already decided that to get their schools working normally they would go ahead and use unvetted staff anyway.

An ongoing issue with relying on List 99 is that it picks up only people accused of misconduct in working with children.

This lets through people even with criminal convictions, if they are entering the education system for the first time.

This was one of the main reasons for bringing in the enhanced checking system.

A similar service in Scotland - known as Disclosure Scotland - is said to have been working without problems, checking people through the Scottish Criminal Record Office.

The system in Northern Ireland has not changed for years and again officials say there are no problems.

Employers obtain police checks from the Police Service for Northern Ireland, either directly, or through the Department of Education, or - in the case of supply agencies - through the Department of Health, Social Services and Public Safety.