Action to cut the number of accidents involving NHS staff is "patchy", according to the public spending watchdog.

The cost to the NHS because of staff signed off sick or payouts for accidents is around £173 million-a-year, concluded a report by the National Audit Office.

That cost is even more when staff replacement costs, treatment costs and court compensations awards are taken into account as well as losses to productivity.

It also found an increase in the number of reported accidents and a widening gap between the best and worst performing trusts.

Most common accidents continue to be needlestick injuries - where someone is cut with a syringe needle - slips, trips and falls as well as exposure to hazardous substances.

The report found that rising cases of work-related stress are also becoming a serious issue with over two-thirds of trusts reporting an increase in the last three years.

Accidents and health issues are critical for a system that employs more than a million people but is constantly constrained by staff shortages.

The NAO found many NHS trusts had got better at reporting the accidents but not at preventing them.Over a fifth of trusts identified staff shortages and increased workloads as being partly responsible for the increase in accidents.

Head of the National Audit Office Sir John Bourn said: "More needs to be done to reduce the number of staff accidents in NHS trusts.

"Good progress has been made through the initiatives such as the Back in Work campaign but too many trusts are still not implementing good practice and there are wide variations in terms of access to counselling and other support to get staff back to work more quickly.

"At a time when it is crucial to recruit and retain staff, the NHS must show that the health and safety of its staff is a top priority."

The report drew an angry response from the Liberal Democrat's health spokesman Dr Evan Harris who warned the "bullying culture" created by central government was a key factor in the problems.

"The high costs of accidents and sickness in the NHS have a massive impact on patient care. There is obviously the cost to the taxpayer of sickness absence. But there is a huge risk to patients when staff shortages occur due to accidents, sickness and stress.

"The increase in work-related stress is the price of the government imposing political targets which do not improve patient care. The sweatshop, bullying culture created by Labour's centralising approach is an obstacle, not an incentive to NHS improvement," he said.