Landline telephone providers face strict new penalties for mis-selling services or switching customers without their consent that could see them forfeit up to 10% of their annual turnover.
Communications regulator Ofcom said telecoms companies will have to abide by the new rules or face the stiff fines.
It is hoped the new rules will prevent companies attempting to gain customers through dishonest activities such as mis-selling and "slamming", where users are switched from one firm to another without their knowledge.
Ofcom said the move with allow for stronger protection of consumers and allow it to take swift and decisive action against providers who break the rules.
Ed Richards, chief executive at the regulator, said: "It is not acceptable for consumers to suffer from companies engaging in dishonest sales and marketing activity.
"Ofcom will not hesitate to take enforcement action against firms who don't comply with the new rules."
The regulator said it receives about 750 complaints a month relating to mis-selling and slamming.
Consumers complain about calls from providers pretending to be another company, providers quoting incorrect package costs and poor information about minimum contract periods and early termination charges.
Ofcom has previously investigated 14 companies for breaching regulations and fined two providers 10% of turnover for failing to comply.