Waiting lists increased to more than 300,000 in April

Andrew Dearden said long waits for treatment are partly responsible for the amount of sick notes written.

Economic Development Minister Andrew Davies said some points were based on anecdotal evidence, not research.

Dr Dearden told AMs some of his report was based on anecdotal evidence and his personal experiences.

Dr Dearden, who chairs the British Medical Association's Welsh GPs committee, told the assembly's economic development committee that 25% to 30% of the sicknotes he issued were given to people waiting for hospital treatment.

We just have to invest the time and money in the way they seem to do in some parts of England Dr Andrew Dearden

He also said there was a clear relation between waiting lists and people staying on the sick.

Dr Dearden said he didn't mind his evidence being called anecdotal, because most anecdotal evidence was based on fact, otherwise it was just stories.

Some 18% of people in Wales of working age have a long-term illness fully or partly preventing them working, 10% higher than in England.

Liberal Democrat AM Jenny Randerson said she regretted criticism by the minister, and it was blindingly obvious that longer waiting lists would lead to more people being off work.

Dr Dearden said before the committee meeting: "We've been asked why GPs have to provide so many sick notes.

"When people are waiting on the waiting lists of the NHS for a year or 18 months, they sit on the sick until they can receive treatment.

Return to work

"Part of the reason is because the NHS has such long waiting lists in Wales."

Dr Dearden said if patients were treated more quickly they could return to work earlier.

Dr Dearden says Wales needs to look over the border into England

But it would be unfair to expect GPs to risk aggravating a condition by sending a patient back to work too early because the NHS in Wales cannot cope with demand.

He added: "Wales has a higher incidence of the disease than the rest of the UK but one of the things that we can fix is the fact that our waiting lists are so long.

"I think we need to look over the border. There are places in England where people wait a month or two to see an orthopaedic surgeon and two or three months to get their hips done.

"It's not impossible because it's being done.

"We just have to invest the time and money in the way they seem to do in some parts of England."

NHS figures for April showed the number of people waiting for treatment in Wales increased from March by more than 8,000, from 294,243 to 302,730.

But Welsh Health Minister Jane Hutt cited shorter waits for treatment in areas such as cardiac and cataract surgery and predicted "even more good news" this summer.