Major unplanned protests have erupted in Brisbane’s CBD, disrupting traffic and bringing parts of the city to a standstill.

Members of the Construction, Forestry, Maritime, Mining and Energy Union (CFMEU) pulled the surprise, and potentially illegal, protests on Thursday morning.

The protests come just one day after the High Court refused to overturn a government takeover which plunged the union into administration.

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Hundreds of members walked off the job and gathered at protest sites around the city, including on Queen St in Brisbane City.

About 500 protesters gathered outside the CFMEU’s Bowen Hills headquarters, chanting as speakers discussed issues faced by workers and protesting against the government-issued administration.

CFMEU administrator Mark Irving told The Courier Mail that the High Court decision is final.

“I have advised staff and members that any action this morning is likely to be unlawful industrial action, and I have directed them to return to work,” Irving said.

“I urge everyone to stay calm and focus on getting on with the job. It is time for all members, delegates and staff to work together to return the Union to membership control.”

Jade Ingham — former National President of the CFMEU and one of 21 leaders who lost their seats along with former CFMEU boss Michael Ravbar — was seen addressing the crowd while members chanted “Stand up, fight back”.

In a statement after Wednesdays High Court decision, Queensland’s Crisafulli government welcomed the decision and used strong language to condemn the CFMEU’s “criminal and violent behaviour”, referring to the union as “thugs”.

“Queensland workers deserve to be safe at their workplaces and paid competitively without being exposed to criminal and violent behaviour, and this is why the Crisafulli Government will always back workers over CFMEU thugs,” the statement said.

“Reflecting the decision today, the Crisafulli Government will continue to crack down on the CFMEU’s lawlessness, violence and aggression to ensure workers and employers are safe, and that building sites are productive as we deliver our record infrastructure pipeline.”

Queensland Police have been contacted for comment.