The most scandal-ridden government ever known?

The Labor government of Australia's largest and most populous state is facing an epic defeat tomorrow after 16 years in power, following a string of scandals possibly unrivalled in the Western world.

Corruption, pornography, drugs, gay sex romps, marital infidelity – the government of New South Wales (NSW) has had them all, and more, in the past two years alone. Now long-suffering voters are determined to wreak revenge, and not even a photogenic premier related to a Booker prize-winning author will be enough to save Labor from its worst post-war electoral drubbing.

"It will be the political equivalent of a slasher movie, a bloody affair in which the bodies of sitting members pile up as NSW voters go on the rampage against a government which... has truly worn out its welcome," predicted David Penberthy, editor of The Punch, a news website.

The beneficiary of the bloodbath will be the leader of the conservative coalition, Barry O'Farrell, a genial but uncharismatic character who has failed to dazzle on the campaign trail. No matter: voters would rather elect a stuffed monkey than endure another five years of Labor sleaze and incompetence.

Ministers have fallen like ninepins since Ohio-born Kristina Keneally – whose husband, Ben, is nephew of the novelist Tom Keneally – became NSW's first female premier 16 months ago. Her transport minister, David Campbell, resigned after being photographed leaving a gay sex club. Her ports minister, Paul McLeay, admitted surfing pornographic and gambling websites at work. Her regional development minister, Ian Macdonald, dubbed "Sir Lunchalot", charged taxpayers for a holiday to Dubai and Italy. The husband of her education minister, Verity Firth, was arrested buying an ecstasy tablet.

Things were scarcely better under Ms Keneally's immediate predecessors, Nathan Rees and Morris Iemma. Mr Rees's police minister, Matt Brown, stripped to his underpants and danced on a green leather couch during a drunken party at Parliament House. His health minister, John Della Bosca, had an extra-marital affair with a 26-year-old woman (he was 53) who claimed they had sex in his parliamentary office.

More seriously, Mr Iemma's aboriginal affairs minister, Milton Orkopoulos, was charged with molesting under-age boys. He was jailed for 14 years in 2008.

And several ministers were implicated in a corruption scandal involving a young and attractive female town planner who approved illegal high-rise buildings in exchange for designer handbags and sexual favours.

The watershed for Labor was the departure of the long-serving premier Bob Carr, a bookish and politically astute man who enjoyed high poll ratings and basked in the glory of the 2000 Sydney Olympics.

Since he retired in 2005, the party's standing has plummeted – and now the only question is the scale of its political wipe-out.

Some commentators are predicting that the party could be left with as few as 15 seats in the 93-member Lower House. Matthew Knott wrote on the Crikey news website: "When it comes to his [Mr O'Farrell's] policy platform, many voters don't know and don't care what's on the table – so desperate are they to pull down NSW Labor's pants on polling day."

The government has even failed to make the trains run on time. Sydney's public transport system was ranked below Mumbai's and Mexico City's in a survey two years ago by the accountancy firm PricewaterhouseCoopers.