Lawyers have endorsed the construction union’s controversial claims that building workers would have fewer rights than ice dealers under new legislation.

But the government has criticised the claims, calling them a stunt because the building regulator has similar compulsory examination powers.

On Sunday the Construction Forestry Mining Energy Union (CFMEU) launched an ad dramatising the fact the Australian building and construction commission (ABCC) bill extends the building regulator’s compulsory examination powers.

In the ad, a stern male figure who remains in shadows tells a soft-faced middle-aged construction worker: “You don’t have the right to remain silent, and you don’t have the right to a lawyer of your choice.”

A bearded man labelled an ice dealer is told: “You have the right to remain silent, and you have the right to a lawyer of your choice.”

It concludes: “If Malcolm Turnbull gets his way, a worker will have [fewer] rights than an ice dealer.”

The CFMEU’s construction national secretary, Dave Noonan, said: “There are basic principles of law and common rights that we’re entitled to as Australian citizens.”

Under the ABCC bill it is an offence punishable by up to six months’ prison not to comply with an order to give evidence. Claims the evidence would incriminate the witness are no excuse not to provide it. However, evidence given cannot be used in proceedings against the witness.

An industrial lawyer and Maurice Blackburn principal, Kamal Farouque, told Guardian Australia the ABCC could compulsorily examine witnesses who had no privilege against self-incrimination.

“This is different to the ordinary criminal situation where people suspected of a crime don’t have to speak to police,” he said. “The ad is accurate in that respect, definitely.”

A criminal lawyer and Stary Norton Halphen principal, Robert Stary, said: “It’s true that everyone charged with a conventional criminal offence has many more rights than a building worker in an industrial dispute.

“The right against self-incrimination and the right to silence are cornerstones of our justice system.”

The employment minister, Michaelia Cash, told the Senate the CFMEU’s ads were based on a false premise and were a “political stunt” because the union had not complained when the current regulator, Fair Work Building and Construction (FWBC), was given compulsory examination powers.

“The ABCC will have the same powers as former prime minister [Julia] Gillard gave to the [FWBC], the same powers that this Senate itself voted to extend until 30th June 2017,” she said.

“They will do anything and they will say anything to ensure that the laws in the building and construction industry are not changed.”

The ABCC’s compulsory powers are similar to those of FWBC, although it needs an administrative tribunal member to approve orders to force evidence.

Australian Industry Group head of workplace relations policy, Stephen Smith, said the comparison between ice dealers and construction workers was “not a comparison that can be validly be made”.

“The best comparison is with other [civil] regulators, like the Australian Securities and Investments Commission [Asic], the Australian Competition and Consumer Commission (ACCC) and the Australian Tax Office,” he said.

“[Compulsory examination powers] are not exceptional when you look at those other regulators. They need to investigate breaches and if witnesses refuse to talk, they’re hampered in that effort.”

The Australian Chamber of Commerce and Industry’s workplace relations director, Richard Calver, said: “You can’t compare an ABCC investigation with a criminal investigation where a suspect risks life imprisonment if convicted.

“Rights are context specific. A person in the building industry risks nothing by cooperating with the ABCC, because the answers they give can’t be used against them unless they fail [to cooperate] or lie.”

Workers are allowed a lawyer of their choice, but the ABCC bill states only that a person “may be represented by a lawyer if the person chooses”.

An employment department spokeswoman said: “The ABCC legislation expressly says that witnesses can be represented by a lawyer.

“Regulators such as the ABCC, Asic and ACCC who have compulsory examination powers have the ability to exclude a particular lawyer to preserve the integrity of an investigation,” she said.

“For example, it may be appropriate for different lawyers to represent witnesses who contradict each other, or to have different lawyers represent a witness to wrongdoing and the person suspected of breaking the law.”

Farouque said the provisions were concerning because the ABCC could take an expansive view of its powers and exclude particular practitioners from representing construction industry witnesses.

On Monday independent senator Jacqui Lambie said she would oppose the ABCC bill in the Senate, citing a lack of oversight for the coercive powers and the ability for the ABCC to exclude a particular lawyer from an examination.

The trade union royal commission recommended the building regulator has compulsory investigatory and information gathering powers equivalent to those possessed by other civil regulators. It said the ABCC bill powers “appear appropriate in this regard”.

Calver said a report on the ABCC had concluded that without compulsory powers its investigations would be thwarted due to the unwillingness of witnesses to cooperate.