There is more trouble for beleaguered Queensland Rail (QR), with revelations more than a dozen staff have been sent packing after failing drug and alcohol tests at work.

The revelations come at a testing time for the organisation amid a timetable crisis, driver shortage and as the State Government looks to replace three board members who resigned last month.

ABC News can reveal 14 employees and one contractor failed drug or alcohol tests at work in the first six months of the year.

All but one are no longer working for the organisation and there is an ongoing investigation into the remaining worker.

QR said the staff were not drivers or guards but employees from Corporate, Citytrain, Travel and Tourism and the Network departments, plus a contractor working on a QR site, but ABC News understands at least one was a senior manager.

QR Chief Executive Nick Easy said the alcohol and drug tests are among the most rigorous in the industry.

"Queensland Rail will not compromise on safety and our employees and contractors are bound by a zero-tolerance alcohol and other drugs policy," he said.

"If an employee returns a positive result, they are immediately excluded from the workplace until a thorough investigation and performance management process is undertaken, including disciplinary action as appropriate."

About 10,000 random drug and alcohol tests are conducted on QR employees every year.

It is not clear how this year's results compare with previous years.

Drug tests can occur randomly, QR CEO Nick Easy says. ( Supplied: ACT Policing )

Opposition Leader Deb Frecklington said the revelations were appalling.

"This behaviour is completely unacceptable and QR should take the toughest possible action against those involved," she said.

"This issue raises more serious concerns about the safety of our rail network.

"Safety should be improving but last year the number of trains running red lights reached a 10-year high."

Transport Minister Mark Bailey said QR staff are required to be fit for work at all times while on duty.

"It is disappointing to hear about any positive results being returned but we are talking about 14 positive results from almost 6,800 full time QR staff."

"I would prefer we were celebrating the fact we had zero positive results being returned but this shows the testing regime is working.

"These staff have been caught and have paid the price by losing their jobs as a result."

Queensland Rail said all staff and contractors know they can be tested at any time.