O2 and Be Broadband saw their combined customer base reduce in size during the last three months, it has been reported.
The firms lost 27,600 subscribers between July and September, leaving the broadband providers with 625,300 customers.
This figure is down six per cent on equivalent point in 2010.
Be Broadband and O2 saw the rate of customer decline accelerate during the third quarter of the year, suggesting more consumers have been switching broadband provider.
A fall of 16,300 customers was witnessed between April and June, following a 2,400 decline between January and March.
Be Broadband recently announced the reopening of its line bonding service, which was forced to shut down in August due to overwhelming demand.
Line bonding works by combining two broadband lines with speeds of up to 24Mb in order to achieve faster download speeds.