Lives could be put at risk by failings in some police forces' plans to deal with civil emergencies or terrorist incidents, a report has revealed.
Her Majesty's Inspectorate of Constabulary (HMIC) says shortcomings in emergency plans in some English and Welsh forces "cannot be acceptable".
The HMIC report calls for concerns to be addressed before the 2012 Olympics.
The report on civil contingency planning was released to the BBC under the Freedom of Information Act.
An HMIC report on Civil Contingency Planning by Forces in England and Wales says the inspectors looked at 22 forces which were seen as having a high risk of a civil emergency.
Catchment areas may include airports, power stations and potentially hazardous industrial sites.
"In all forces reviewed, a terrorist attack is a possibility," the September 2009 report said.
It looked at the capacity of the forces to deal with civil emergencies and said the majority performed well.
But it said some forces, which have not been named, failed to come up to standard "where failures potentially represent a vulnerability of service or risk to the public".
It found that one in 10 forces did not have "robust plans to mobilise officers" while more than 40% "failed adequately to test these plans in exercises".
"Enough forces deal with civil contingencies for HMIC to ask why a minority do not," says the report.
"The majority of forces have plans and policies in place for business continuity, though only a few are making satisfactory progress with their arrangements.
"Such shortcomings cannot be acceptable - forces must be able to deliver essential services during periods of disruptions."
Problems the report identified:
- At one force the chief officer had not attended a key regional contingency planning meeting for over a year - breaching Association of Chief Police Officer's (Acpo) minimum standards
- One force had not identified its key policing functions - which would be needed to keep going in the event of an emergency
- Some force's local approach to the issues led to a "fragmented, inconsistent approach" to emergency planning. Bedfordshire and Hertfordshire police's appointment of a continuity manager was praised for helping them to avoid this problem
- Half the forces had not conducted "no notice" exercises - seen as the best way to test the response of officers to civil emergencies - within the previous 12 months
- Some forces - Merseyside, British Transport Police and Leicestershire - are strong on learning from debriefs after civil emergency exercises, but others do not, "raising the risk that they will repeat past mistakes"
It said as a matter of urgency Acpo should, with the support of the Home Office, "map out accurately the ability of forces to support one another at major incidents or events, and at the Olympics".
Co-operation between regional forces should be encouraged, it said.
The 22 forces have not been named by HMIC, but other forces believed to have been involved in the inspection were: Lancashire, South Yorkshire, Humberside, West Midlands and the Metropolitan Police.
The inspections took place between 2008 and 2009.
A spokesman for ACPO said: "The service is always looking to improve its response to the public and individual forces will look carefully at the issues identified here.
"HMIC's role is to push the service towards continuous improvement and this report was intended to assist as we prepare for the challenge of policing the 2012 Olympics.
"This HMIC report, in its analysis of 22 forces, highlights areas where forces are performing successfully individually and collectively and recognises that in the bulk of incidents, police forces respond well."