The high court today rejected a bid by an anti-abortion group to prevent pharmacies from dispensing the morning-after pill without a doctor's prescription.

The health secretary, Alan Milburn, has allowed women over the age of 16 to buy emergency contraception directly from the pharmacist since the beginning of last year. But the Society for the Protection of Unborn Children (Spuc) had wanted the court to declare that he had acted outside his powers.

It had argued that allowing pharmacists to dispense the morning-after pill amounted to "procuring a miscarriage" - a criminal offence under the 1861 Offences Against the Person Act.

Rejecting the society's challenge as "erroneous", Mr Justice Munby said the future of most forms of contraception, affecting millions of people, was at stake.

He said: "In my judgment Spuc's legal argument is erroneous. Spuc's application must be dismissed. In my judgment the prescription, supply, administration or use of the morning-after pill does not - cannot - involve the commission of any offence under either section 54 or section 59 of the 1861 Act."

He added there would be something "grievously wrong" if a judge "in 2002 were to be compelled by a statute 141 years old to hold that what thousands, hundreds of thousands, indeed millions of ordinary, honest, law-abiding citizens have been doing day-in, day-out for so many years is and always has been criminal".

The judge said he was glad to be spared "so unattractive a duty".

The case raised "medical and legal questions of great complexity, difficulty and interest ... also moral and ethical questions of great importance".

The judge said it was "no exaggeration to say that the outcome of this case may potentially affect the everyday lives of hundreds of thousands, indeed millions, of ordinary men and women in this country".

He added that, whatever the society might say, its allegations of criminality did not only concern the morning-after pill but also "any form of birth control which may have the effect of discouraging a fertilised egg from implanting in the lining of the womb - that is to say, not merely the morning after pill but also IUDs, the mini-pill and even the pill itself".

Family planning experts had warned that the action, if successful, could have criminalised millions of women who use various forms of contraception.

The judge said the social case put by the Family Planning Association (FPA), and supported in all particulars by the health secretary, "remains wholly unanswered by Spuc".

He said: "I cannot see that it is any part of the responsibilities of public authorities, let alone the criminal law, to be telling adult people whether they can or cannot use contraceptive devices of the kind which I have been considering.

"It is, as it seems to me, for individual men and women acting in what they believe to be good conscience, applying those standards which they think appropriate, and in consultation with appropriate professional ... advisers, to decide whether or not to use IUDs, the mini-pill and the morning-after pill.

"It is no business of government, judges or the law."

Spuc's lawyer, Richard Gordon, had said before the ruling: "Neither choice, nor consequences can justify the destruction of a human life once it has started fertilisation."

More than a third of all emergency contraception is now dispensed by pharmacists. Two versions are available - Levonelle-2, a high-dose progestogen pill, and Schering PC4, a combined oestrogen-progestogen pill.

The morning-after pill is taken in two doses and can be effective if taken up to 72 hours after unprotected sex. If it is taken 48 hours after sex, its effectiveness drops from 95% to 58%, and falls further if taken after 72 hours.

Anti-abortion groups argue that over-the-counter sales encourage promiscuity and increase the spread of sexually transmitted diseases, and that the primary function of the pill is to destroy life.

But manufacturers of the morning-after pill said fears that handing out the pill through chemists would encourage underage sex had not been borne out. Figures showed the average age of buyers had been 24, with 85% aged over 20.