“Casual” employment will be defined and a universal standard spelled out for casuals to convert to full or part-time employment in industrial relations legislation introduced this week.

Separately, the government is making a fresh effort to take on the militant elements of the Construction, Forestry, Maritime, Mining And Energy Union, with a bill to enable parts of the union to “de-merge” from it. This follows deep fractures within the union over the behaviour of construction heavyweight, John Setka.

The industrial relations package, which will also contain changes to facilitate enterprise bargaining, comes after tripartite negotiations between the government, unions and business.

Neither business nor unions will agree with all of it. There will be a Senate inquiry and further tooing and froing, and its fate won’t be decided until next year.

The existing definition of a “casual” is considered too general and lacking in clarity, and so subject to court interpretation.

Under the new Commonwealth statutory definition, a person will be defined as a casual if employment is offered “without any firm advance commitment” that it will continue indefinitely and follow an agreed pattern, and the employee accepts it on that basis.

The strengthened process for converting into full or part time employment will be an enhancement of existing rights of conversion under some awards. It will make the right to convert from casual to permanent available to all casuals.

An employer must make a conversion offer if

• the employee has worked for the employer for a year and worked a regular pattern of hours for the past six months (previously 12 months)

• the employee could continue to work as a full or part time worker without significant change to their hours

• an employer may decide not to make an offer or accept a request if they have reasonable grounds.

If a worker declined an initial conversion offer, they would retain the right to request every six months.

The IR package will also quash the potential for “double dipping” opened by a federal court finding that regular casuals are entitled to a range of paid leave entitlements, and employers can’t use the casuals’ extra pay to offset that.

Casual rates are normally some 25% higher to offset the fact these workers don’t have various paid entitlements. The minister for industrial relations, Christian Porter has claimed the court decision could cost business up to $39 billion in back pay.

The legislation will ensure businesses do not have to meet this back pay, and prevent future double dipping.

It will enable employers to offset amounts already paid via casual loadings against any claims for benefits to be paid.

The pandemic put the issue of casual employment front and centre. The risk of the virus spreading in the aged care and health sectors was increased because many of these workers have several jobs.

The court decision further complicated the issue of casual workers.

“We cannot do nothing when we have a situation where employers are delaying making hiring decisions because of ongoing confusion about the legal status of casual employment,” Porter said.

“Similarly, Australia’s 2.3 million casual employees need certainly about their work arrangements and entitlements,” he said.

He conceded the government’s definition of casual employment would be broader than some business groups wanted, while unions would want it broader still.

Porter said the changes to casual conversion rights struck a balance, “ensuring those working regular shift patterns who want greater job security can convert … while maintaining the existing rights for employers to refuse such requests if there are reasonable grounds for doing so”.

Under the proposed legislation for union de-mergers, the Fair Work Commission will be able to approve an application for a ballot to withdraw from an amalgamation after five years. At present five years is the cut off.

The CFMMEU’s mining and energy division secretary, Tony Maher, had discussions with Porter about the plan, which would allow his division and also the manufacturing division to quit the union, which has been wracked by the disruptive behaviour of the construction section.

Earlier efforts by the government to deal with the militant element of the union have failed.

Maher recently resigned as the union’s national president; Michael O'Connor, brother of Labor frontbencher Brendan O'Connor, also recently resigned as national secretary. He remains head of the manufacturing division.

Porter said “the appalling behaviour of the CFMMEU has driven some divisions within that organisation to consider their options”.

He said the legislation, if passed, would mean “decent, hard-working parts of an amalgamated union that are dissatisfied with the state of their union will have an opportunity to leave, if that is their wish”.

The move triggered another round of infighting in the union.

Dave Noonan, CFMEU construction secretary, said in a Sunday statement: “Tony Maher did not inform the CFMMEU, the ACTU nor any other union about his secret meeting with Christian Porter. He still hasn’t told anyone what deals he has done with the Attorney General and the Morrison Government.

"The government will use this bill to divert attention from the Industrial Relations Omnibus Bill it is putting to Parliament … which is the beginning of a march back to WorkChoices.”

Maher on Sunday made it clear he would press for a demerger if there was the opportunity.

“If the bill passes through parliament and a new union structure is available that would put mining and energy workers in a better position, then we have an obligation to put it forward to members for their consideration,” he said.

“The Mining and Energy Division’s Central Council has instructed us to look at all options for our future direction.”

“Disamalgamation provisions should be more workable. It’s a weakness of the current legislation that unions can only demerge within a narrow time window, regardless of the circumstances. It’s undemocratic.”

Maher said he was “regularly in dialogue with the federal government on a range of issues affecting my members, and the current highly restrictive demerger laws are among the issues I have raised”.