A union strike at its Geelong refinery could mean a threat to its operations if there is no intervention made by Shell on the cleaners' job security.

Twenty specialist cleaners hired at the Geelong refinery will consider a walk-out on their jobs despite arguments on wages, according to the Liquor Hospitality and Miscellaneous Workers Union.

"We call on Shell to urgently intervene and help defuse this crisis by ensuring these workers' jobs are secure," Jess Walsh of LHMU Victoria.

The cleaners decontaminate safety working clothes by refinery workers.

The cleaners were employed by Spotless but ISS (Integrated Service Solutions) Cleaning argued that they won a contract to provide cleaning services. There is speculation that 20 workers will consider a walk-out.

The LHMU also alleged that ISS will cut the worker's pay by 36 per cent.

LHMU said a strike at the refinery will halt fuel transfers to Victoria.

However, a Shell representative cleared out that fuel supplies in Victoria and Tasmania will not stop. The refinery produces 116,000 barrels of oil a day and distributes to petrol stations in both areas.

Shell Australia spokesman Paul Zennaro said a probe will be conducted to ISS regarding the matter.

"We expect a seamless transition between the two contracts and don't anticipate any impact of production for the refinery," Mr. Zennaro said.

On the other hand, Darryl Prince of ISS Cleaning said it will discuss with both the union and with Fair Work Australia "to ensure there is no disruption to the client."

Mr. Prince adds that ISS is considering to offer a full-time employment with several of the current employees and is currently waiting for the responses of the individuals.