The WA Opposition has accused Premier Mark McGowan of billing taxpayers more than $12,000 for a trip to Sydney during which he headlined a $3000-a-head "intimate dinner" to raise money for NSW Labor.

But Mr McGowan said the primary purpose of the two-night visit was to meet NSW Infrastructure Minister Andrew Constance and the head of Infrastructure NSW.

Taxpayers were billed $12,000 for Premier Mark McGowan's two-night trip to Sydney during which he headlined a NSW Labor fundraiser.

During the trip, he also met with NSW Labor leader Michael Daley, former Prime Minister Bob Hawke, former WA Premier Geoff Gallop and former NSW Premier Bob Carr.

Mr McGowan missed WA Parliament to take the Sydney jaunt.