Users in Doncaster, North Wales and Bristol were affected by the outage.
British Sky Broadcasting (BSkyB) has admitted that it had overloaded its broadband service, which has led to customers experiencing slower-than-normal broadband speeds.
A Sky spokeswoman told the BBC that, "Following a combination of an underlining increase in network traffic as well as a high rate of new customer additions, we are aware of capacity issues in a small number of exchanges."
"We are working on adding new capacity to those exchanges as quickly as we can. We apologise to all customers who have been impacted by this issue," the spokeswoman said.
Users in Doncaster, North Wales and Bristol were affected by the outage and service in these areas fell from 13-14Mbps down to as low as 2Mbps.
Sky said that less than 5% of their broadband customer base were affected by the slower broadband speeds.
Recently, Sky unveiled a new subscription service, Sky Go Extra, which will allow customers to download the latest films from Sky Movies and content from channels such as Sky 1 and Sky Atlantic.