Western Sydney voters will no longer be taken for granted.

The historically blue-collar region that was once a Labor surety has transformed into a battleground characterised by marginal seats.

And with the down-to-the-wire NSW election just two weeks away, both major parties know it.

Deputy NSW Labor leader Prue Car and former Liberal minister Stuart Ayres have told the Western Sydney Leadership Dialogue the area will decide the next government.

"Where western Sydney goes, so will NSW," Mr Ayres said on Thursday.

The former minister for western Sydney is facing a tough contest in his electorate of Penrith, where he holds a wafer-thin 0.6 per cent margin in the third-tightest battle in the state.

Greater Western Sydney has one of the fastest-growing populations in Australia and the third-largest economy.

Both major party leaders were on the campaign trail there on Thursday, with Premier Dominic Perrottet visiting Parramatta and Labor's Chris Minns stopping by Riverstone - underscoring the importance of one of the largest regions in the state.

Former NSW Labor leader John Robertson says the area's voter base has shifted over the decades.

"The seats that were taken for granted should historically have been Labor seats. But that's not the case any more," he said.

"It's much more marginal now in western Sydney. The electorates are much more volatile."

Jodie Brough, a partner at lobbying firm SEC Newgate, says the close margins are driven in part by the similarities between both parties' policies.

"It's spy versus spy," she said.

"They announce something over here that sounds pretty Labor then the coalition announces something that also sounds pretty Labor.

"If you're a voter out there, you might be having trouble looking at the two parties and seeing what the differences actually are."

Across the last few elections, the region's voting patterns have changed with demographic shifts.

Ms Car believes western Sydney is now a "microcosm of the state".

"That's why it tends to reflect the way the government goes in almost every election."

Of the five most marginal seats in NSW, three - East Hills, Leppington and Penrith - are in Sydney's west.

In Riverstone and Holsworthy, which maintain margins of roughly six per cent, politicians have attempted to win over the growing Indian diaspora by courting community representatives.

Last month, the premier visited a Hindu temple in Kings Park, while the opposition leader met with the Hindu Council of Australia last year.

The major parties have also promised billions for western Sydney infrastructure projects, but Ms Brough says it is unclear if these commitments will pay off.

"You can't necessarily predict where people are going to go," she said.

"The reality is that people do not have the loyalties they once had to major parties. They are more questioning of their political leaders and I don't necessarily think that's a bad thing."