A key claim supporting the NSW government's business case for a new western Sydney stadium was never agreed to by the NRL, a parliamentary inquiry has been told.

The business case for the $300 million redevelopment of Parramatta Stadium anticipated that 30 NRL games would be played at the new venue.

But the sport’s second-in-command on Monday said the league had never agreed to that.

“We haven’t given any commitments of that nature,” NRL chief operating officer Nick Weeks told the NSW parliamentary inquiry.

“Where our clubs play their matches will be a matter for clubs to determine.”

Lynda Voltz – a Labor MP and member of the Public Works Committee, which is holding the inquiry – accused the government of inflating figures to justify their stadium spend.

“This is what the government has done – they’ve over-inflated figures, the NRL says they didn’t provide these figures,” Ms Voltz said.

“Where did 30 games come from if the NRL didn’t provide them those figures?”

The government originally planned to knock down and rebuild Parramatta, Allianz and ANZ stadiums at a cost of well over $2 billion but has since scaled-back the scope of the works.

Premier Gladys Berejiklian in March back-flipped on the demolition of ANZ stadium, choosing to instead refurbish the venue at a cost of $810 million – saving $500 million.

The total stadium spend now stands at $1.8 billion for the three venues.

A joint parliamentary inquiry was launched in April to scrutinise how the strategy was developed, its economic justifications and possible impact on communities.

Mr Weeks told the inquiry that Sydney had suffered from years of under-investment in sporting infrastructure.

“Unfortunately decades of under-investment and a scattergun approach, driven by political interests rather than coherent policy, has resulted in a network of stadia in Sydney which is dilapidated,” he said.

“It does not provide the world-class experience our fans, members and players deserve.”

Former NSW Liberal leader John Brogden, the Office of Sport, KPMG, Venues NSW, the Sydney Olympic Park Authority and the City of Sydney have all previously addressed the inquiry.

The new Parramatta Stadium is currently under construction and is due to be opened in mid-2019.

NSW Sports Minister Stuart Ayres says it’s up to clubs to decide where they play.

“Government has no role in directing which events are held where,” Mr Ayres said in a statement.

“We’re investing in the best facilities to ensure Sydney and NSW is the number one destination for sport and major events.”

By Tom Rabe