Australia's biggest construction union will carry out safety audits on Lend Lease sites across the nation.

In the wake of last month’s fire at the Barangaroo development site in Sydney, the Construction, Forestry, Mining and Energy Union announced on Tuesday it is investigating safety procedures for workers.

CFMEU national construction secretary Dave Noonan said that the union had a responsibility to ensure the safety of workers on Lend Lease sites, following evidence of poor safety practices in relation to fires on two sites in NSW.

A Lend Lease crane collapsed during a fire at the University of Technology Sydney at Ultimo in late 2012.

Following a re-ignition of the fire at Barangaroo on March 21, a Lend Lease spokeswoman said “safety remains our No.1 concern” and “evacuation procedures were followed”.

On Monday the CFMEU was hit with an “unprecedented” $1.25 million fine for illegally blocking workers from Melbourne building sites.

The union was fined and ordered to pay costs for ignoring court orders that outlawed the blockades at Grocon’s Emporium site.

Victorian Supreme Court Justice Anthony Cavanough said only the hefty fine would do justice to the blatant defiance of the court.

The CFMEU has maintained its conflict with Grocon was over safety issues.

“We cannot leave the safety of our members to chance and that’s why we have taken the decision to audit every Lend Lease site,” Mr Noonan said in a statement on Tuesday.