A peak body in the resource sector believes the maritime union is preparing to stage strikes similar to those of 2009 and 2010, which cost the sector $750,000 a day.
The Australian Mines and Metals Association fears the Maritime Union of Australia's bid to extend a 30-day period in which it can lawfully take industrial action is a sign of imminent and damaging industrial strife.
AMMA acting chief executive Richard Berriman attacked the MUA, claiming strikes were part of the union's strategy during negotiations with marine contractor Tidewater.
"The union's conduct has been a deliberate, calculated and cynical attempt to construct a series of unreasonable demands and then justify to their rank and file taking of strike action," he said.
"It is very difficult for employers to bargain 'in good faith' with the MUA given its disingenuous approach."
Both parties believe the outcome of the Tidewater agreement is of crucial importance, because it will effectively become a template for 19 other agreements covering 2500 workers.
In a sign the year-long negotiations have taken a toll, MUA assistant secretary Will Tracey returned fire.
"AMMA is blatantly misleading the public as a part of an ongoing political campaign to demonise the MUA and the union movement generally," he said.
"While the MUA has been authorised to take industrial action by Fair Work Australia, we have no current plans to do so and have, in fact, sought an extension of time, so that we can try to reach a negotiated outcome."
AMMA has offered 16.5 per cent more money over four years.
The MUA said it reduced original demands for 6 per cent annually over four years to 5.5 per cent, as a show of good faith.
It is understood there are 20 sticking points. One is the union's demand for employers to exhaust the local workforce before hiring foreign crews. The union wants the roster changed from five-weeks on and five off, to a more family-friendly four-on, four-off.
The workers won 30 per cent over four years in their last deal.