The concerns from the Police Federation of Australia, the ambulance union and nurses' federation have been raised to a Senate committee examining the Coalition's bill to change the Fair Work Act to give volunteers a voice in workplace agreements.

Paid Victorian CFA firefighters have told the committee about the need for seven paid firefighters to be deployed to any fire, citing cases where volunteers were slow to respond and in which having just four firefighters was inadequate.

In January, Hoppers Crossing paid staff were sent to a house fire in which a man suffered burns to 90 per cent of his body and a mother and a baby were trapped inside.

With just four firefighters on the scene, a decision was made to go into the house, while neighbours hosed the man down. The man later died in hospital.

The submission says it took 10 minutes for another crew to arrive, and had there been more firefighters there the incident could have been better managed.

The case is included in the brigade's submission to the Senate inquiry, which began hearings in Macedon on Monday.

In response to the CFA crisis – in which the volunteers' association says the deal for 800 paid CFA staff would undermine their role – Prime Minister Malcolm Turnbull introduced laws that would change the Fair Work Act to give volunteers the power to make submissions during negotiations between paid staff and employers.

The bill will also add an objectionable clause to workplace laws that will make it unlawful for a workplace agreement to undermine the capacity of volunteers.

Some submissions have accused the government of over-reach and formulating legislation based on politics not policy, with wide-reaching consequences beyond the CFA dispute.

More than 400 volunteer community emergency response teams are used by Ambulance Victoria in rural locations where a low workload does not justify the presence of permanent paid paramedics.

The ambulance union says they provide an excellent service, but under the proposed laws these people would have a say in the workplace agreement for the state's 3500 paramedics.

The union warns that if the bill is passed, volunteers could interrupt or delay improvements to patient care that happen through EBA negotiations, which "adversely impact the standard of care provided to the community by paramedics".

Arguing against the bill, the Police Federation said including volunteers in police staff negotiations would cause "great concern for policing".

Victoria Police and the AFP use volunteers in non-operational roles.

"The proposed provision will likely only serve to hinder and restrict police forces from encouraging the use of volunteers," PFA chief executive Mark Burgess wrote.

There have been hundreds of submissions to the inquiry; many of those published on the website come from concerned volunteers who, in passionate submissions, address fears of a union takeover.

"Some of their [union] claims are downright discriminatory, like bringing back apartheid, and I can't believe government ministers would tolerate this, so I urge you to fix the problem and dismiss the union's log of claims," one submission says.

In another, a veteran volunteer says he has seen incidents in which career firefighters have stood down from fighting a fire on union orders.

The saga has caused major rifts between some volunteers and paid firefighters that are threatening to boil over, as well as causing great angst in the Andrews government.

The previous CFA board, management and then Victorian emergency services minister Jane Garrett also had concerns about the effect the EBA would have. All lost their jobs as a result.

The firefighters' union says the new agreement will vastly improve firefighter and community safety.