The media owner has struck a deal with Simplifydigital to create guardiandigitalcomparison.co.uk.
It will promote the new service to the readers of The Guardian, The Observer and guardian.co.uk, with in-paper advertising and a free phone number.
Tina El-Hage, ventures business manager at GNM, said: "We are delighted to be able to offer our readers and online users this fantastic new price comparison service.
"The site enables customers to easily compare thousands of different packages in terms of both their price and their quality, and check their current broadband speed, alongside relevant editorial content on guardian.co.uk."
In August, GNM pushed ahead with plans to create a club for its most loyal readers offering exclusive content and invites to events.
