UnionsACT secretary Matthew Harrison said the Australian union movement would never be intimidated nor threatened by acts of violence.

"The attacks on the CFMEU office in Melbourne can only be described as despicable and reprehensible acts of mindless violence by people that are not reflective of the construction industry," Mr Harrison said.

"Thankfully, there has been nothing to suggest that we could see similar scenes here in Canberra."

Mr Harrison said the union movement was built by working people committed to equality, unity and fairness.

"These values are antithetical to the ideologies of those organising these attacks," he said.

Chief Minister and ACT Labor leader Andrew Barr said he was not concerned there would be an infiltration of the union movement or any protests by far-right groups in the ACT.

"We're not exactly a hotbed for far-right activism," Mr Barr said.

The Australian Council of Trade Unions has said unions have been targeted by extremist groups sowing seeds of division and doubt about vaccinations among workers.

Compliance with COVID-19 safety regulations on ACT building sites in the ACT is understood to be generally strong, along with strong take-up of vaccinations.

Chief health officer Dr Kerryn Coleman has confirmed there have been cases of the virus being transmitted on construction sites, but said the rules did not need to be tightened.

The ACT government has repeatedly ruled out introducing a vaccination mandate for the construction industry in the territory, with high vaccine take-up expected without a mandate.

Mr Barr on Wednesday said forward bookings for vaccine appointments showed the ACT was on track to get 95 per cent of its eligible population vaccinated.

Unions and employers in the ACT have strongly encouraged construction workers in the ACT to get vaccinated against COVID-19.

Master Builders ACT chief executive Michael Hopkins said the construction industry had responded strongly when called on by Mr Barr to get vaccinated.

"We're aware that some individuals require longer to consider vaccinations or may have medical reasons that prevent them from being vaccinated," Mr Hopkins said.

"We support that being their choice, and we don't see any reasons why the local building construction industry won't do its bit to get the ACT above the 80 per cent double vaccinated target."

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The Master Builders association earlier this month organised a drive-through AstraZeneca vaccination hub in Fyshwick for tradespeople.

A national survey, conducted by the Melbourne Institute at the University of Melbourne, found construction and utilities workers had the highest proportion of vaccine hesitancy of any industry group.

Mr Barr last week said a series of COVID-19 restrictions breaches on residential construction sites were unforgivable, but stressed mandatory vaccines were not needed for the sector due to overwhelmingly strong take-up across the ACT.

"I appreciate everyone wants to know every single person they might come into contact with in a high-risk setting would be vaccinated. It is generally the case that most people are now [vaccinated] in those settings," he said at the time.

Residential construction was shut for a month after the ACT was locked down on August 12. Large-scale construction sites returned to work on Friday, September 3, and residential construction projects resumed on September 10.

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