A housepainter was taken to hospital with suspected spinal injuries and broken bones after a four-metre fall from a ladder at a house he was painting in O'Connor.

The incident follows an accident last Thursday at a Woden worksite where a 20-year-old apprentice electrician suffered an electric shock and fell five metres from a ladder on to a concrete pavement. On the same day, 600 building workers rallied in Civic, demanding better workplace safety following four workplace deaths in Canberra in 10 months.

Doctors treating the fourth-year apprentice say his condition has improved from ''serious'' to ''stable'' in recent days.

WorkSafe Commissioner Mark McCabe said the latest injury happened at lunchtime yesterday while the painter was working alone on a house in the inner north suburb. He reiterated a plea for workers and bosses to take care at work.

''While details are sketchy, it appears that a worker fell three or four metres from a ladder while working alone painting at the home,'' Mr McCabe said.

''He has been taken to hospital awaiting results of X-rays.

''Late last week I reminded workers to remain vigilant about safety in their workplaces after an electrician suffered serious injuries when he fell five metres onto a concrete floor.''

Mr McCabe's inspectors will be at a Braddon demolition site this morning investigating allegations of serious safety breaches in the handling of asbestos on the job.

The building union has stopped work on the central Canberra building site, alleging that a load of rubble contaminated with the dangerous material had been rejected at the Mugga Lane tip because it was not sealed properly.

Construction, Forestry, Mining and Energy Union members stopped work at the hotel redevelopment at 78-80 Northbourne Avenue, saying basic asbestos safety procedures were not being followed.

The union's branch secretary Dean Hall said workers on the site had not been trained and proper safety gear was not being used.

''There's heaps of issues,'' he said.

''Some of the workers weren't wearing safety gear and were exposing themselves to the contamination, and there was no decontamination. Blokes were coming off the site, jumping in their cars or utes and going home to their families without proper decontamination.

''Then there was a large skip full of waste rejected from the Mugga tip because it wasn't sealed properly.

''We just hope that fibres weren't flying off this thing all the way from Civic to Symonston and back.''

The contractor on the site could not be contacted for comment.

Mr McCabe said his inspectors had visited the site last week and found some ''issues'' but nothing serious enough to warrant a shutdown or to issue an improvement notice.

He said WorkSafe would be back on the site this morning to investigate the union's allegations.

''We identified with some issues to do with the removal of asbestos and they were addressed to our satisfaction,'' the commissioner said.

''We heard yesterday afternoon from the CFMEU of some further issues that they allegedly found on the site.

''The union has supplied us with some photos and we think that there might be a strong case for something not being done right there.''

He is hoping to hear the full story in a meeting with both sides today.