Sussex Police are stepping up security checks on officers and staff to prevent corruption and the leaking of information.

Extra vetting has begun on the 600 staff and officers who regularly have access to sensitive information or details about covert operations.

Force vetting manager Jeff Saunders said the police service had a poor record for leaks.

He said: "The majority of staff are honest but research and experience of corruption have shown that forces up and down the country must become proactive in protecting sensitive assets and detecting corruption.

"Vetting is one important tactic to achieve this aim."

All staff are checked for such details as criminal records. The extra vetting has been brought in after recommendations from HM Inspectorate and the Association of Chief Police Officers' task force on corruption.

It comprises more in-depth questionnaires on personal and financial backgrounds to determine whether some employees become vulnerable to corruption.

Mr Saunders said they could result in one or two people being asked to change jobs within the force so they have no access to the sensitive information.

The Sussex branch of the Police Federation has expressed support for the vetting but has reserved the right to challenge the process if it felt someone had been unfairly treated.

Federation spokesman Graham Alexander said: "We do have concerns about wider philosophical issues including how the information is gathered and how the vetting system itself is controlled, but generally the procedure is in line with guidelines."

Mr Saunders said the impact of corruption was out of proportion to the very small numbers of staff involved and could cause serious harm to police operations and public confidence.

Detective Superintendent Dick Barton stressed the process was a deterrent against corruption and would protect those most vulnerable.

He said: "It will also give people greater confidence to challenge and report any approaches made to them from unauthorised disclosure of information."

Further security measures being introduced include "protective marking" for handling and storing sensitive information.