NHS staff in Scotland are taking more time off work sick - despite targets to cut absenteeism.

Health service phoneline NHS 24 has the highest illness rates, with the average worker off one day in 10 last year.

This is against a rate for the entire workforce of one day off sick in 18 and a target of one day in 25.

Mary Scanlon, Conservative health spokeswoman, said the data, released yesterday, was a matter of concern.

When NHS 24 took on calls to GPs outside surgery hours at the end of 2004, it struggled to cope and patients had to wait hours for nurses to ring them back with advice. However, last year, it appeared to have turned the corner.

Ms Scanlon said: "I would hope the government will look into the cause of those figures at NHS 24. An absence rate of around 10% has to signal wider issues."

A spokeswoman for the phoneline said they were aware of the problem. She said: "Our workforce provides a service to the public more than 90% of the time in the out-of-hours period and this presents particular challenges for us. However, we are addressing issues in relation to absence and have early indications, from the figures for April and May, both of which are around 6.5%, that we are starting to have a positive effect."

The staff sickness rate for NHS Scotland was 5.55% during the year to April 2007, up from 5.23% the previous year. The increase occurred despite the Scottish Executive asking health boards to draw up plans to reduce absenteeism as part of their efficient government savings drive.

Glyn Hawker, Scottish organiser for health with trade union Unison, said the introduction of a new pay and conditions deal for NHS staff had increased the burden on employees and may have affected sickness absence.

She stressed higher absenteeism is expected in the health service because of the desire to avoid spreading infections to patients. Ms Hawker said: "Unison always has concerns about whether targets are realistic and whether meeting the target becomes the issue - come what may, it seems targets will be met regardless of the impact on health and wellbeing."

The last Scottish administration had hoped cutting absence in the health service would free up money spent hiring short-term staff cover. However, the use of temporary nurses by NHS Scotland also increased last year.

The hiring of nurses and midwives from private agencies rose by 7.4% - although the bill dropped by £8m because more companies who had signed deals to supply the health service were used. Reliance on the NHS's own nurse bank also rose by 25.8%, increasing this cost by more than £9m.

Ross Finnie, Liberal Democrat health spokesman, called on the executive to recruit more nurses to the core workforce. He said: "Bank nursing is not a cost-effective method of staffing the NHS. The executive must commit to recruiting more nurses to ensure taxpayers' money is put to the best possible use."

Health Secretary Nicola Sturgeon expressed her disappointment at the numbers of non-registered agency staff being used in our hospitals.

An executive spokeswoman said: "Reducing staff sickness absences across the NHS in Scotland is important, both for patient care and for all NHS staff. The partnership between the NHS boards and health unions, backed by Scottish government support, is vital if we are to implement the right policies and processes to reduce staff absence."