One in four pregnancies ends in an abortion each year, global estimates from the World Health Organisation and Guttmacher Institute suggest. The report in the Lancet said 56m induced abortions take place annually — higher than previously thought.

Researchers acknowledge rates have improved in many rich countries but warn this masks no change in poorer areas over the past 15 years.

Experts are calling for new approaches to contraceptive services.

Researchers point out that abortion rates were similar across countries — regardless of whether terminations are legal or not.

It is possible that some are not aware of the contraceptive services available or come from countries where abortion rates are higher in general, researchers say.

Dr Bela Ganatra, from the WHO, said: "Investing in modern contraceptive methods would be far less costly to women and to society than having unwanted pregnancies and unsafe abortions."

Many women said they chose not to use contraceptives because they were worried about side effects, felt stigmatised or thought there was a low risk they would become pregnant.