Members of the public sector union Unison are angry at shift changes they say will be imposed upon them from next Monday and as many as 900 members from West Yorkshire could strike.

They say the changes could lead to some working a seven day week amounting to 63 hours.

Police chiefs said the old shifts did not meet the needs of the job and were wasteful.

Unison are balloting on strike action and the decision will be known by the end of next week.

The staff affected include police community support officers, police station help desk staff, detention officers and communication workers.

Rachel Hemingway, the joint secretary of Unison's West Yorkshire Police branch, said: "Unison is extremely angry and disappointed by the actions of the Chief Constable, Sir Norman Bettison, who has chosen to impose a new shift pattern on its members.

"Unison believes the changes are nothing more than a cost cutting exercise and one that is based on 'more for less'.

"The change will leave Unison members tired, demoralised and suffering from ill health. The changes will include seven-day working and a 63 hour week.

"Unison believes these savage measures and cuts to a public service will not deliver an improved service to the public."

But West Yorkshire Assistant Chief Constable David Evans said: "People tell us they want more officers on the street.

"The new shift patterns let us do that by having new neighbourhood police teams working until 11pm seven days a week."

"The old shift pattern couldn't give us this and was wasteful, with staff working overlaps during the day, not when most needed."