Iran's parliament is seeking a ban on vasectomies and a tightening of abortion rules as the country moves away from its progressive laws on family planning in an attempt to increase the birthrate.

Two decades after Iran initiated an effective birth control programme, including subsidised male sterilisation surgeries and free condom distribution, the country is to make a U-turn.

Last year the supreme leader, Ayatollah Ali Khamenei, criticised existing policy on contraception, describing it as an imitation of western lifestyle.

The 74-year-old has urged the government to tackle what he believes to be an ageing population and to double the number of people in Iran from 77 million to at least 150 million.

This week Tehran's conservative-dominated parliament, the Majlis, voted to discuss banning vasectomies and introducing punishments for those involved in encouraging contraceptive services and abortions, local agencies reported.

The semi-official Fars news agency reported that an overwhelming majority of Iranian MPs had consented to consider the bill. Given the influence of Khamenei among MPs, the proposals are likely to pass.

"If we move forward like this, we will be a country of elderly people in a not too distant future," Khamenei said in October, according to Fars. "Why do some [couples] prefer to have one … or two children? Why do men or women avoid having children through different means?

"The reasons need to be studied. We are not a country of 75 million, we have [the capacity] to become at least 150 million people, if not more."

Khamenei has made similar remarks in a number of speeches, prompting authorities to slash subsidies for vasectomies and curb the government budget for family planning programmes. Under Mahmoud Ahmadinejad's presidency, the government promised free gold coins if couples had more babies.

Kamiar Alaei, a Harvard University alumnus who has been jailed in Iran along with his brother for pioneering Aids treatment, expressed concern that the U-turn would cause a rise in the number of women who died in childbirth.

Alaei said the blame for the slow birthrate lay with social, economic and cultural hurdles preventing Iranian youth from marriage and making babies, rather than the country's successful family planning policies.

"More than half of the population consists of young people between the age of 20 and 30 … but they are not able to procreate because social, economic problems are stopping them from marriage," he said. "The blame should be on those problems, not a policy that has worked quite well."

About 70% of Iran's 77 million people are under 35.

After the 1979 Islamic revolution Iran's population doubled within 10-11 years, to almost 60 million, as authorities encouraged a baby boom in light of the eight-year Iran-Iraq war, Alaei said.

The family planning policies initiated in the 1990s brought the growth under control.

"We have enough young people who will procreate when they marry in the coming years," Alaei said. "Slashing contraceptive services altogether will only increase unintentional abortion and maternal mortality."

It is not clear whether the health ministry approves of the parliamentary bill but it would be unlikely to challenge Khamenei's view on the issue, at least publicly.

Despite this, Iran holds relatively progressive views on issues such as fertility treatment, stem cells, surrogacy, sex-change operations and contraceptive services, most of which is heavily government-subsidised.