Karmarama already handles Plusnet’s advertising, having won the business in 2010 following a competitive pitch.
Plusnet’s CRM work was previously handled by OgilvyOne, which has had the direct marketing account for BT since 2001. OgilvyOne will continue to work on the main BT CRM account.
Sarah Pepworth, the head of marketing at Plusnet, said: "As our business has evolved, so has Karmarama’s and so we’re delighted to be able to benefit from their integrated approach to communications, as well as their experience and understanding of our business."
Last year Karmarama created the "broadband that loves you back" campaign, which positioned Plusnet as an internet provider that cares about customers, as opposed to selling the brand with claims about connection speeds.
This year will see the next phase of the campaign rolled out, and Karmarama said the consolidation would allow Plusnet to "deliver a much richer and consistent customer journey through the line".