Figures released last week predicted that Britons would spend more than £1bn on cosmetic surgery in 2008.
"Pressure tactics" in the name of discount deadlines are adopted by cosmetic surgery clinics to exploit the people's craze, says consumer magazine Which?
There are at least eight such clinics breaking industry rules, says the magazine.
One is offering a £500 discount on breast enlargement if the operation is carried out by the end of December.
Industry guidelines state that cosmetic surgery clinics "must not offer discounts linked to a deadline date".
Websites for the companies mentioned by Which? carry details of the offers concerned.
One of the companies criticised was Surgicare which is offering £500 off breast enlargement procedures booked and taken before the end of this month.
It is also offering £200 off eye bag removal and three treatments for the price of two if they are undertaken before the end of January 2008.
The Harley Medical Group is offering discounts of up to £100 for laser hair removal treatment booked by the end of this month.
And The Hospital Group is advertising a £400 saving on any procedure carried out before the end of December.
Which? says choosing to have cosmetic surgery is "a major and potentially life changing decision" and it is "highly irresponsible" of clinics to rush people with time-sensitive discounts.
Independent Healthcare Advisory Services (IHAS) guidelines state: "Advertisements must not offer discounts linked to a deadline date for booking appointments or surgery or other date-linked incentives."
Jenny Driscoll, a health campaigner at Which? told BBC Radio Four that she hoped the industry would take note of the findings.
"We really hope that they will stop this pressure advertising which can rush people into surgery and treatments which they probably might not need, and also may cost them thousands of pounds and may end up being a waste of money," she said.
Which? says it has written to the IHAS and the companies involved.
"What is the point of having a code of practice if companies are going to ignore it?" Ms Driscoll said.
"This is yet another indication that proposed self-regulation will not work for the cosmetic treatments industry."
Which? says it wants the government to use the coming Health and Social Care Bill to introduce tighter regulations for the entire cosmetic treatment industry.