The biggest contribution UK couples can make to combating climate change would be to have only two children or at least have one less than they first intended, argues an editorial published in the British Medical Journal.

Family planning and reproductive health expert Professor John Guillebaud and Dr Pip Hayes, a GP from Exeter, call on UK doctors to break their silence on the links between population, family planning and climate change. They point to a calculation by the Optimum Population Trust that "each new UK birth will be responsible for 160 times more greenhouse gas emissions … than a new birth in Ethiopia."

As far back as 1949 The Royal Commission on Population stated "We have no hesitation in recommending…a replacement size of family in Great Britain" and called for a "continuous watch over population trends and their bearing on national policies". Yet the UK continues to this day without any defined population policy.

With world population exceeding 6700 million, Guillebaud and Hayes say that humankind's consumption of fuel, water and food is exceeding supply. They add that the 79 million annual increase in global population equates, somewhere in the world, to a huge new city for 1.5 million appearing each week.

Providing contraception does not need to be coercive, they argue, asserting strongly that governments do not have to follow the example of India in the 1970s or currently China.

Many countries, including Costa Rica, Sri Lanka and Thailand, have reduced their fertility rates by meeting women's unmet fertility needs and choices. The authors claim that with half of pregnancies worldwide being unplanned, no-one needs to be forced to use contraception, what they need is information and access.

The reality is, say the authors, that most women in low resource settings want to be able to plan fewer children than they have, but are prevented from doing so because of many barriers. These include lack of empowerment and abuse of their rights by husbands, partners, mothers in law, religious authorities or sometimes even contraceptive providers. The evidence shows that the demand for contraception increases when it is made available and accessible.

Professor Guillebaud and Dr Hayes call on doctors to help eradicate the many myths and non-evidence based medical rules that deny women access to family planning.