British couples should consider having no more than two children to help reduce the environmental impact of the rising global population, doctors have said.

An editorial in the British Medical Journal today calls on GPs to encourage the view that bigger families are as environmentally dubious as owning a patio heater or driving a gas-guzzler.

Writing in the journal, John Guillebaud, professor of family planning at University College, London and Pip Hayes, a GP based in Exeter, urge doctors to "break a deafening silence" over the use of family planning to curb the rise in population, which has been viewed by many in the community as a taboo subject.

Managing the impact of a soaring human population will be one of the most politically fraught issues governments will have to grapple with in coming decades. Although the rate of population growth has slowed since the 80s, the UN estimates the world's population has increased by about 76 million a year this century, which drives up greenhouse gas emissions and exacerbates the destruction of wildlife habitats.

Previous efforts to limit population growth in India in the 70s and in China, with its one child policy, have made any attempt to raise the issue in Britain highly controversial.

The authors call on schools and GPs to develop education programmes to explain how a rising population is environmentally unsustainable, and how families who have no more than two children will help ensure the population remains steady or even falls.

Government figures for 2007 show that average fertility rates in England and Wales were 1.91, meaning there were 191 children born for every 100 women, but that rate has been rising since 2001.

Guillebaud argues that bringing the fertility rate down to 1.7 would lead to a halving of the population within six generations.

"Should we now explain to UK couples who plan a family that stopping at two children, or at least having one less than first intended, is the simplest and biggest contribution anyone can make to leaving a habitable planet for our grandchildren?" the editorial asks. "We must not put pressure on people, but by providing information on the population and the environment, and appropriate contraception for everyone ... doctors should help to bring family size into the arena of environmental ethics, analogous to avoiding patio heaters and high-carbon cars."

The authors emphasise that couples should never be coerced into having fewer children than they wish, but the environment should become part of a couple's decision making. The doctors, both of whom are linked to the Optimum Population Trust, a thinktank that researches the impacts of a rising population, claim that every new birth in the UK produces 160 times more greenhouse gas emissions than one in Ethiopia.

"We are not criticising those people in Britain who had large families in the past, because a lot of people had no inkling about the sustainability implications," Guillebaud told the Guardian. "The decision that needs to be made is one that balances rights. It's people's right to have the size of family they choose, but surely that should be balanced against the rights of future generations."

But the debate is complex, as a sharply falling population would have considerable economic, fiscal and social impact.

The editorial calls for improved availability of contraceptives in the developing world, where the biggest rises in population are anticipated. The authors cite the impact of widely available contraception in countries such as Costa Rica and Iran, which have cut their fertility rates.

Chris West, director of the Environmental Change Institute at Oxford University, said that while there were good environmental reasons for halting the rise in human population, it would not deliver sufficient cuts in greenhouse emissions quickly enough. "If we had a way to reduce the population ... it would be one way to address climate change, but in the current circumstances, it's not a very effective way," he said. "For all sorts of other reasons ... we probably need to be aiming at zero population growth, but it's not going to deliver emission reductions on anything like the timescale we need."

Backstory

Humans have struggled with overpopulation since antiquity, when the Greeks were forced to set up colonies across the Mediterranean to reduce pressure on resources back home. According to some accounts, they also encouraged sexual abstinence, delayed fatherhood and introduced basic forms of abortion. In modern times, India began to control its population growth in the 50s in an attempt to alleviate poverty, but stepped up efforts in the 70s, with education programmes and state-sponsored birth control. In China it is estimated that the one-child policy brought in during the late 70s has prevented nearly half a billion births. In many countries, simply providing contraception has been enough to bring fertility rates below the figure needed to maintain a stable population, as people choose to have fewer children. In his 1729 satirical pamphlet, A Modest Proposal, Jonathan Swift suggested that Irish families might alleviate their poverty by choosing to sell their children to the rich for food. But nothing has been as effective in reducing the human population as the flu virus. The 1918 strain is believed to have killed more than 20 million people.