Mr Howard was fine despite needing to be "rescued by police" on Thursday after inadvertently coming across a group of angry union members protesting against cuts to penalty rates.
The 77-year-old former Liberal leader had been attending a conference on Pitt Street when he walked out onto the street to find dozens of people shouting, booing him, holding up CFMEU flags and making profane gestures.
Footage on social media shows Mr Howard having to walk several hundred metres along the city street, flanked by a number of NSW police, as noisy protesters repeatedly chanted "The workers, united, will never be defeated".
Mr Howard appeared to take the incident in his stride, continuing to walk along the streets until the mob returned to the rally.
While the former PM had initially been shocked, NSW Police "came to the rescue" to move him away and he was "fine", a spokesman for Mr Howard told AAP.
Mr Turnbull later tweeted: "I condemn CFMEU's thuggish harassment of John Howard today. A reminder of why ABCC is needed. Bill Shorten should condemn CFMEU as well."
Late on Thursday the CFMEU issued a statement saying: “ The rally was peaceful, but loud".
"From the footage we have seen, it appears some protesters made their views known to Mr Howard about anti worker laws he introduced while Prime Minister as a result of which, he lost an election and his seat," the statement said.
The CFMEU, supported by other unions, held rallies in capital cities on Thursday to protest against what the union says is the federal government's "attacks on working people".
Tens of thousands attended the union-led events attacking the reintroduction of the building industry watchdog and cuts to penalty rates.
ACTU president Ged Kearney, who didn't see the incident but heard about it, told AAP "there is a lot of anger against John Howard because of WorkChoices".
People attend a penalty rates protest rally in Melbourne. (SBS News) Source: SBS News
"It's the sort of feeling, you've got Work Choices Mark II with this [Turnbull] government," she told AAP on Thursday.
"The good thing about today was that thousands and thousands of workers turned out to stand together."
She attended the rally in Sydney and addressed the workers.
“All to deliver power to the great big corperations who are desperate to maximise their profits at the expense of your blood sweat and tears,” she said.
In Melbourne, more than 10,000 gathered at the Victorian Trades Hall Council and marched to Liberal Party headquarters, where CFMEU state secretary John Setka voiced his disapproval of the ABCC and recently announced cuts to some weekend penalty rates.
“Construction workers and people working in cafes and hospitality industry are second class citizens that's what they have made this country at the moment,” he said.
Hotel cleaner Margarita Murraysterk said the loss of penalties would cost $2000 of her annual $30,000 wage.
“One is the food for our children one is for our public transport and more importantly for the security of our life,” she said.
Others, like nurse Jess Mengel attended the rally fearing the penalty rate cuts could be broadened.
“It's the hospitality industry at the moment but it'll be us soon,” she said.
More rallies are expected in coming weeks.
