Oil giant Esso is planning to scrap the offshore workplace agreement for its oil and gas operations in the Australian Bass Strait, potentially wiping out decades-old union conditions, in order to introduce new employee rosters.

The move, set to happen this week, could reignite a four-year dispute between the employer and trade unions. Mediation between the parties was cancelled recently due to a legal technicality.

An Esso spokesperson said: “We remain committed to reaching a resolution and have been offering a generous wage increase in our discussions with unions in exchange for improvements in productivity and flexibility in rosters that are considered standard for the oil and gas industry.”

The principle trade unions involved – the Australian Manufacturing Workers Union (AWU) and the Electrical Trades Union (ETU) – are now considering further strikes that could begin as early as Tuesday.

In rewriting the current offshore workplace agreement, Esso wants to introduce a 14 days on, 14 days off roster for its offshore workforce in an attempt to cut labour costs by reducing changeovers necessary for its current seven days on/off roster.

The company also wants to remove overtime caps of 75 hours per year and scrap manning levels for catering staff. In exchange, Esso has offered an annual pay increase of 3%, not including backpay. The last pay increase came in 2014.

Unions have spoken out against Esso, saying the company has failed to improve workers’ accomodation on the offshore platform as a condition of the extended rosters.

ETU organiser Peter Mooney said workers are demanding better meals and single-room accomodation. Currently, offshore staff are required share rooms with up to four people.

He said: “We’d be happy to consider 14:14 rosters but Esso needs to improve conditions of work on the platforms to reach industry standard.”

Esso has previously been forced into negotiations when, back in 2016, the Government of Victoria intervened to terminate unions’ indefinite industrial action as it began to threaten the state’s gas supplies.

Last year the High Court ruled that the AWU’s work bans were ‘not protected’, breaching a Fair Work Commission order that resulted in the union losing the ‘privilege’ of protected action during the rest of the negotiations.