TWU national secretary Tony Sheldon said yesterday some petrol tankers posed a real threat due to poor maintenance and drivers being pushed too hard.

Mr Sheldon said the TWU was concerned these issues would lead to further incidents like last year's fatal accident at Mona Vale, where a tanker was involved in a crash that killed two men and injured five others.

That tanker was part of the Cootes fleet, which subsequently had more than 100 defect notices issued for its vehicles.

The TWU has lodged a complaint with the Road Safety Remuneration Tribunal over allegations of lack of maintenance and of drivers forced to speed, drive long hours and falsify log books.

"Industry research shows one in four petrol tanker drivers are pressured to drive too fast and half have been pressured to skip rest breaks between shifts," Mr Sheldon said.

"Thirty-three per cent of drivers also report they've been threatened with job losses if they report serious safety flaws.

"Even worse, 45 per cent of drivers say their employers routinely delay brake maintenance, with one saying his tanker was 13,000 kilometres overdue for servicing."

Acting secretary for the TWU's Wollongong sub-branch, Nick McIntosh, said there were no fuel depots in the area but that didn't mean the Illawarra was safe.

"They don't base themselves in Wollongong but they do definitely deliver to petrol stations throughout Wollongong and the Illawarra," he said.