The NSW government says union demands for safety upgrades to a new train fleet are unreasonable and will cost taxpayers $1 billion, but guards claim commuters would be put at risk.
The $1 billion cost would come on top of the $30 million per month the government is already paying to warehouse the New Intercity Fleet (NIF).
On Thursday, Finance Minister Damien Tudehope announced he had cancelled all talks with the Rail, Tram and Bus Union, shattering five weeks of intensive negotiations led by Transport Minister David Elliott.
Secretary of the RTBU Alex Claassens said the government were playing political games with a serious safety issue.
"(It was) very disappointing listening today to (Treasurer) Matt Kean and Damien Tudehope, trying to turn this into a political issue when it's clearly not," Mr Claassens told reporters on Friday.
"It's never been a political issue."
Union members first raised safety concerns about the NIF fleet when it was ordered by the Berejiklian government from South Korea in 2016.
Rail Guard Craig Turner, who has inspected the NIF fleet, said guards would not be able to hear people calling for help if they became trapped.
"Don't forget it's all about hearing as well," he said.
"The organisation wants to put the guard inside the train without the door opening.
"We will not be able to hear women or children screaming."
On Friday Mr Tudehope said the union had not gone through appropriate processes with the regulator to raise its safety concerns, insisting the trains were safe.
Mr Tudehope said he would not submit the claims to the expenditure review committee to alter the trains, calling them the "most advanced technology comparable to anything in the world".
The $1 billion dollar figure was put together by Transport for NSW, and suggested upgrading costs included $385 million in direct costs, approximately $420 million in delay costs and $27 million in additional planning costs.
"Let me be very clear. This government does not want to flush any money down the drain," state treasurer Matt Kean said.
"There's $2 billion worth of rolling stock sitting in mothballs behind me rusting on the tracks because of these unreasonable demands from the union."
Mr Elliott said he is waiting for an audit of the billion dollar figure, but he intends to prosecute the union's request to the government's ERC.
"In my good faith arrangements with the union I said, 'I can't guarantee that ERC will agree to all of your requests'," Mr Elliott said Friday.
"But I have given them a good faith commitment that I will prosecute their claims."
Mr Claassens said the transport minister's commitment to have the $1 billion scrutinised made good sense, and he had not heard the figure before Thursday.
Opposition Leader Chris Minns said any claims the treasurer made about the costs to upgrading the NIF needed to be substantiated.
"One of the big problems here is that these trains should have been built in Australia, made by Australians," Mr Minns said, adding that the fleet was constructed in Korea.
"These trains are already two years late and $1 billion over budget."
"Under the premier's predecessor, Gladys Berejiklian, we had a decade's worth of industrial peace, because common sense and maturity when it comes to these sorts of negotiations took place," he added.
"That is not happening under the premiership of Mr (Dominic) Perrottet."
Australian Associated Press
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