Official figures published by the former Portuguese colony showed that gaming revenues fell 2.6 per cent year-on-year to 351.52 billion patacas (USD 44 billion) in 2014 - the only decline since annual figures were first released in 2002.
Last month's takings were especially dire, plunging a record 30.5 per cent year-on-year to 23.285 billion patacas - marking a seventh consecutive month of decline and the biggest drop since the gambling hub began recording monthly revenues in 2005.
"It has had a negative impact on the VIP playing sentiment significantly," she told AFP.
Macau is the only part of China where casino gambling is legal, and the industry is dependent on big spenders from the mainland.
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But high-rollers have been reined in by the anti-graft drive, which has seen Xi vow to crack down on high-ranking officials - described as "tigers" - along with low-level "flies", in a campaign which includes curbing lavish spending.
A slowdown in the mainland economy has also been taking its toll on casino earnings.
Experts had predicted that growth in the VIP segment, accounting for two thirds of the total revenues of Macau's gaming industry, would be limited by the continued focus on corruption.
Beijing is also reported to be clamping down on illicit funds channelled from the mainland through its casinos.
Revenues hit a yearly record in 2013 at USD 45 billion, official figures showed.
Macau overtook Las Vegas as the world's casino capital in terms of revenue after the sector was opened up to foreign competition in 2002, and now enjoys gambling revenues multiple times that of the American city.