Fewer men are going for a vasectomy
Reservations about the irreversible nature of vasectomies may explain the sharp fall in the number performed by the NHS in England over the past decade, say experts.
NHS Information Centre data and hospital episodes statistics show the vasectomy rate has more than halved.
There were 15,106 performed in 2011-12, compared with 37,700 in 2001-02.
The British Pregnancy Advisory Service (Bpas), who compiled the statistics, says the findings are "disappointing".
Bpas chief executive Ann Furedi said: "Vasectomy is a safe and reliable method that gives men the opportunity to play an active role in contraception.
"It is disappointing that the only long term method which enables men to play this part is declining.
"We must ensure that all couples who want to use this method can access it promptly on the NHS, while recognising that it won't be for everyone."
The declining number, which does not include those carried out at private clinics, could be prompted by a number of factors, including increasing awareness among men that a relationship may break down, amid the rise of second families.
Restrictions on funding and greater emphasis on contraceptives for women, such as hormonal and copper coils, may also contribute.
Bpas says the decline might be one reason for a recent increase in abortion rates among older women - a 10% rise between 2001 and 2011.
Rebecca Findlay, of the Family Planning Association, said there were many possible explanations for why fewer men were going for vasectomies.
"There is some restriction in the NHS provision and some men may be going privately, but we can't say how many.
"Also, couples are also putting off having children. They might be in their 40s when they decide to try for their first or second baby and this could have a knock-on effect."
Vasectomy involves severing the tubes that carry sperm. The operation is meant to be permanent. There are reversal operations but they are not always successful and they are rarely provided by the NHS.