Ron Whiley, managing director of SWEB Gas - the gas trading arm of South West Electricity - said he was "devastated" by the allegations, which had been passed on by householders to the watchdog Gas Consumers Council.
The complaints come just weeks before domestic gas supplies are opened up to competition in south-west England on 1 April.
About 500,000 consumers in Devon, Cornwall and Somerset will become the first in Britain to be offered the chance to switch from British Gas and take their supplies from another company.
A number of new companies, including SWEB, have engaged in a fierce battle to win customers from British Gas in the past few weeks.
The GCC, which has referred the accusations to the Devon Trading Standards Office, said that complainants' allegations included:
t Being asked to "just sign here, we'll fill in the details and send you more information". Consumers then believe the form is only a request for information when it is actually a contract;
t Verbal promises of higher discounts than those available;
t Use of intimidating language such as, "you are about the only person in the area who hasn't signed up with us";
t No copy of the signed document left with the customer and no mention of a "cooling-off" period.
Ian Powe, director of the GCC, said: "Any trace of aggressive and unscrupulous marketing must be stamped out if competition is not to be devalued.
"We are disappointed that, despite SWEB's earlier promises to tighten quality control of marketing, some sales people have apparently continued to behave irresponsibly."
Mr Whiley said: "One complaint is one complaint too many. This is an extremely serious business and I will be investigating personally."
The company's direct selling operation has been running since November 1995 and 40,000 potential customers have been contacted. SWEB Gas says it has signed up over 30,000 customers so far through a number of channels, including doorstep sales.
Mr Whiley said salesmen were bound by a code of conduct which specifically prohibits false inducements or pressures.
Steve Butterworth, of Devon Trading Standards, confirmed that he had received a number of complaints. "They will be followed up to see if there is any substance to these allegations."Reuse content