Ms McKay says leaked emails from the private ferries contractor TransDev reveal the Sydney ferry replacement program would source 13 new vessels from China and Indonesia.

An email from TransDev managing director Alan Fedda, sent on Tuesday, said three new emerald class ferries would be introduced on the F1 Manly route, with a new fleet of 10 river class vessels to replace the current SuperCats and HarbourCats.

The three emerald class vessels would be constructed in China, while the river class vessels would be constructed in Indonesia, all under the management of Australian shipbuilding company Birdon.

Birdon will source all major components such as engines, propulsion train and electronic equipment in Australia, the email states.

But Ms McKay says it's a "savage blow" for workers in the Hunter, mid-north coast and Sydney areas, where "ferry-building capacity exists".

"This is a kick in the guts to our local manufacturing workforce," she told reporters in Sydney.

"We should be building these ferries here in NSW and, if anything, exporting our expertise to the rest of the world."

However, Transport Minister Andrew Constance says the purchase of the ferries was previously announced in February.

"Jodi McKay spent the dying days of the last Labor government as a cabinet minister ordering trains from China," he told reporters on Wednesday while labelling her a hypocrite.

The last ferries to join Sydney's fleet were six vessels built by Incat Tasmania and delivered in between 2016 and 2017.

"Our preference is Australian manufacturing, but at the same time we have to recognise we do need to get product to market, services to market," Mr Constance told reporters.

Mr Constance said the Berejiklian government would create 100,000 jobs over the next four years through public investment in infrastructure.

He also accused the union movement of "killing" Australian manufacturing by driving up input costs.

Australian Associated Press