Output in the sector contracted at the fastest pace (36.3) since February 2021, when the UK was last in lockdown.
The drop was caused by demand – represented by new orders – falling for a fourth consecutive month (38.5) as consumers reined-in discretionary spending amid rising inflation.
Overall, five of the 14 UK sectors tracked saw output grow in September (vs three in August), while the same number saw new orders grow (vs three in August).
Elsewhere, the tracker showed that overall input cost inflation for businesses intensified in September for the first time since May (77.4 vs 76.6 in August).
The increase was driven by rising energy prices for manufacturers, reported by a record number of firms, surpassing a previous peak during the 2008 oil price shock.
Jeavon Lolay, head of economics and market insight at Lloyds Bank Corporate and Institutional Banking, said: "Inflation returned to double digits, reaching 10.1% in September.
"While we expect UK inflation to remain stubbornly high in the coming months, there are clear signs of an easing in pipeline cost pressures in our latest UK Sector Tracker report."