By the midday break, the blue-chip CSI300 index <.CSI300> was down 2.3 percent at 3,101.16 points, while the Shanghai Composite Index <.SSEC> was off 1.5 percent at 2,560.74, shrugging off Beijing's latest attempts to bolster the country's markets.
"A-shares are being led by corporate earnings, and we expect third-quarter earnings growth to show a bigger slide than mid-year reports, with the main board showing an even clearer decline," analysts at Huatai Securities said in a note, adding that they see little room for a rebound in the near term.
Data released on Saturday showed that profit growth at China's industrial firms slowed for a fifth straight month in September as sales of raw materials and manufactured goods further ebbed.
But consumer firms led the declines on Monday, with a sub-index of the CSI tracking consumer firms <.CSI300CS> plunging 8.4 percent.
The financial sector sub-index <.CSI300FS> fell 1.8 percent, the real estate index lost 1.4 percent and the healthcare sub-index slid 2.4 percent.
The smaller Shenzhen index <.SZSC> was down 1.25 percent and the start-up board ChiNext Composite index <.CHINEXTP> was weaker by 0.08 percent.
Distiller Kweichow Moutai, the country's most famous producer of fiery liquor baijiu, fuelled the broader consumer slump, falling by the daily limit of 10 percent after it reported sharply slower profit growth in the third quarter.
Among other distillers, Wuliangye Yibin also fell by the 10 percent limit, while Luzhou Laojiao was 6.26 percent lower.
A rise in utility companies limited declines in Hong Kong. H-shares listed in Hong Kong <.HSCE> fell 0.4 percent to 10,013.84, while the Hang Seng was down just 0.07 percent to 24,701.05.
Around the region, MSCI's Asia ex-Japan stock index <.MIAPJ0000PUS> firmed 0.4 percent while Japan's Nikkei index <.N225> was up a similar amount.[MKTS/GLOB]
China's yuan fell slightly against a firmer U.S. dollar, with traders continuing to debate whether the central bank will allow the currency to fall through the sensitive 7-to-the-dollar level, which could risk a spike in capital outflows and put further pressure on the economy and financial markets.
At 0420 GMT, the yuan <CNY=CFXS> was trading at 6.9538 per dollar, weaker than Friday's onshore close of 6.9948 per dollar.
(Reporting by Andrew Galbraith; Editing by Kim Coghill)