LOS ANGELES — The worst summer for home sales in decades also put a chill on foreclosure sales, even as the average discounts on the distressed properties got bigger compared with other types of homes.

Foreclosure sales plunged 25 percent in the July-September quarter versus the April-June period and tumbled 31 percent from the third quarter last year, foreclosure listing firm RealtyTrac Inc. said Thursday.

Sales of non-foreclosed properties fell 29 percent sequentially and nearly 31 percent from the third quarter last year, the firm said.

The decline in sales of bank-owned properties and other homes in some stage of foreclosure is in line with an overall housing market slowdown that took hold after federal homebuyer tax credits expired in April.

The fallout over foreclosure processing errors that prompted some lenders to temporarily halt sales of bank-owned homes wasn’t a significant factor in the sharp third-quarter drop in foreclosure sales, said Daren Blomquist, a RealtyTrac spokesman.