Ofcom has fined TalkTalk £750,000 for making an excessive number of abandoned and silent calls, the regulator said.
Ofcom said the telecommunications provider made 9,000 silent and abandoned calls to potential customers between February 1 and March 21, 2011 through two of its call centre operators.
The fine follows an investigation as part of Ofcom's monitoring and enforcement programme aimed at reducing harm caused by such calls.
Ofcom's investigation found that TalkTalk exceeded the limit of abandoned calls organisations can make four times in 2011 during one of its telemarketing campaigns.
It also failed to ensure that information messages were played, meaning consumers received silent calls. As a result, TalkTalk made approximately 9,000 silent and abandoned calls.
During a separate marketing campaign, TalkTalk did not adequately follow Ofcom's policy by failing to make a "reasoned estimate" of the accuracy of its answer machine detection (AMD) technology and also failed to keep adequate records to demonstrate compliance.