A study carried out in the Trent valley region found that girls were becoming pregnant despite receiving contraceptive advice from GPs and in many cases being prescribed the pill.
The study, carried out by doctors at the University of Nottingham, looked at the medical history of 240 girls who became pregnant.
It found that three out of four had discussed contraception with their GP in the preceding year while 121 girls had been prescribed the pill.
The UK has the highest rate of teenage pregnancies in western Europe, with 101,500 teenagers conceiving in 1998.
On average one in three teenage pregnancies end with an abortion. The Trent study found that termination rates were lower than the national average with almost one in four girls opting for an abortion.
However, the study found that of those who chose to terminate their pregnancy, most had a record of seeking emergency contraception.
They were also less likely to have sought medical advice on contraception or to have been prescribed the pill.
The authors said that this showed how important it was for doctors to follow up patients who request emergency contraception.
"Teenagers who choose this method, however, may be at risk of unintended pregnancy, possibly, because it is a marker of 'risk-taking' in sexual activity.
"This emphasises the importance of appropriate follow-up to address long-term needs for contraception whenever a teenager consults for emergency contraception."
Writing in the latest issue of the British Medical Journal, they added that it raises questions about whether people other than doctors should be allowed to provide emergency contraception.
Pill without prescription
The Department of Health is piloting a programme which allows pharmacists to sell the morning after pill to women without a doctor's prescription.
Writing in the same issue, Professor Basil Donovan from the University of Sydney suggested that teenage girls were incapable of taking the pill every day at the same time as prescribed.
He added: "For teenagers, contraceptive choices are complicated by the fact that sexual intercourse is often sporadic, unexpected or coerced."
Prof Donovan suggested that doctors should consider prescribing alternative contraception to teenage girls.
He said more permanent forms of contraception like the IUD or coil, which is inserted into the womb, may be better.
"If teenagers could take their fertility control somewhat for granted during the most precarious stage of their sexual careers, then the ability to negotiate other complex aspects of their sexual well-being could be enhanced."
Anne Weyman, chief executive of the Family Planning Association, said young people should be made aware of different contraceptive methods.
"It may be that oral contraceptives which rely heavily on human memory are not best suited to teenage lifestyles.
"Other methods such as an implant or an injection are highly effective and can be stopped at any time."
A spokeswoman for the teenage sexual health charity Brook said: "We recognise that more needs to be done to ensure that they are given the time and support to use chosen contraceptive methods and advice effectively.
"Brook firmly believes that GPs need both the time to devote to young people and the training to enable them to deal confidently and sensitively with them.
"Given this, young people will be better equipped to make well-informed contraceptive choices and more effectively use the contraceptives they are given."