The AFL grand final could be postponed or even cancelled after MCG security guards won the right to strike on the sport's showcase day, their union says.

The Liquor, Hospitality and Miscellaneous Union was given the go-ahead to take strike action on Grand Final day after a hearing in the workplace tribunal, Fair Work Australia, on Wednesday.

The spat is over pay with an angry LHMU claiming MSS guards, who provide entry point, ground and player security at the stadium, are paid as little as $16.12 an hour.

LHMU security union assistant secretary Ben Redford said MSS was playing "hard-ball" with its employees.

"Guards are angry and upset that MSS' ruthless stance could cause such serious disruption to the community," he said in a statement.

"Guards do not want to go on strike but MSS is forcing them down this road.

"For over six months guards have tried to negotiate with MSS for fair wages, in line with other major contractors, ISS and Wilson.

"But MSS has told guards they can stay on poverty wages.

"MSS can save the footy finals, simply by putting a fair deal on the table for its low-paid guards."

The LHMU said the strike not only threatened the AFL finals, including the September 26 grand final, but could also "wreak havoc" across the state.

"In Melbourne, major office towers, bank branches and data centres risk being shut down. Petrol supplies could be restricted and hospital closures could force sick patients to go home," Mr Redford said.

He also said student safety at La Trobe and Monash universities would be jeopardised, while factories such as Mars Snackfoods in Ballarat and Ford and Holden in Geelong risk closure.

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