He added that new steps being taken by mobile broadband providers like 3 and T-mobile could also affect the market.
Mr Phillips explained: "As the pool of customers completely new to broadband dries up, providers have to devise new ways of tempting consumers away from their rivals. Broadband remains very competitive where it is bundled with other services.
"Affordable and reliable mobile broadband from the likes of 3 and T-mobile could really shake things up in the fixed line market."
BroadbandChoices.co.uk, which powers the broadband comparison facility on Switchwise.com, is an online service designed to help consumers make an informed decision on their internet service.
The comments from the service's product director have come after regulator Ofcom urged ISPs to be clearer on the speed of their connections when promoting new offers.
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