People are still being conned into switching, claims BT
BT wants the telecoms regulator Ofcom to stop rogue operators stealing its customers by mis-selling landline deals.
The phone company says half a million households each year are duped into signing up with another operator.
It says the culprits are usually salesmen claiming to be from BT, who trick people into switching.
The mis-selling, known as "slamming", could be stopped by each home having a telecom pin code, BT says.
It argues that switching should only take place if the code has been given by a customer to the new supplier.
John Petter, managing director of BT's consumer division, said rogue operators had been engaging in deception for at least five years.
"The process we're proposing will put an end to mis-selling misery for good, protect consumers and safeguard fair competition," he said.
"Ofcom's own data shows that a consumer protection pin code would eliminate mis-selling," Mr Petter added.
Earlier this year Ofcom announced a variety of measures to stop the mis-selling of both fixed and mobile phone services.
The regulator said it was looking at making its rules tougher still, but doubted BT's suggested solution.
"We have concerns that a process which requires consumers to contact their existing provider before they switch [such as a pin based process] may impede switching and the benefits to competition which flow from easy consumer switching processes," said an Ofcom spokesman.
The regulator had been receiving more than a thousand complaints a month from people whose phone service had been switched without their permission.
It said its new rules against "slamming" had cut the number of complaints it had received to fewer than 700 a month.
And it said it had taken action against some operators, including the Post Office, Axis Telecom, Economy Calls, Lo-Rate Telecom and Unicom.
BT's argument has received the backing of trading standards officers.
"We're very much in favour of the telecoms industry adopting the consumer protection pin code system," said Ron Gainsford, chief executive of Trading Standards Institute.
"We believe that it will stamp out at source the sort of rogue trading practice that has been plaguing telecoms consumers."