Consumers that are protected from the misselling of fixed-line voice call services will also be safe from those offering voice and broadband services using local loop unbundling (LLU) technology, as a result of a set of Ofcom rules.

Misselling of services using LLU, where third party operators put their equipment in BT's exchanges, is when customers are switched from one company to another operator without their consent. This marketing activity is also known as 'slamming'.

In May 2005, a new condition was introduced by Ofcom for a two-year period, meaning that providers of fixed-line voice call services had to establish and comply with a code of practice for sales and marketing in line with Ofcom's guidelines.

These regulations have led to eleven providers being openly investigated, including Tesco, FreeCall and Economy Calls. Between January and March this year 1,200 complaints were received by Ofcom, so the agency has decided the rules will still apply after the planned cut-off date this month.

Ed Richards, Ofcom chief executive said: "We want competition and choice to continue to grow and we want consumers to benefit from these changes. Consumers need to be able to shop around with confidence. Extending these rules and our enforcement activity will protect consumers from inappropriate sales and marketing techniques."

The company expects that because of the growth of voice over IP (VOIP), further guidelines related to this will also be introduced.

Ofcom is also carrying out separate review of migrations, switching and misselling across services such as broadband and mobile to reveal whether a common approach to switching would benefit consumers. The results of this will be available later this year.