Women embarking on the festive party season are being invited to stock up on free supplies of the morning-after pill.

The British Pregnancy Advisory Service (BPAS) has launched a service where women can request the pill over the phone and get it delivered free of charge to their home.

The charity says the move will help women prevent unwanted pregnancy over the Christmas and New Year period. The service will be available while stocks last throughout December.

The morning-after pill is most effective if taken as soon as possible after unprotected sex, preferably within 12 hours, but it can be taken for up to 72 hours after intercourse.

BPAS said women face barriers obtaining the pill, including not being able to get appointments, some health workers refusing to provide it and the £25 cost if bought direct from a pharmacist. It says these issues are made worse at Christmas, when chemists and surgeries may be closed.

Women wishing to obtain the pill in advance can fill out a form at www.santacomes.org. They leave their details and a time at which they can be called in privacy by a specially trained nurse.

In a 15-minute consultation, the nurse will assess the age of the patient and ensure the pill is not being requested for immediate use. Women will also be told how to take the pill and what to expect. The pill will then be despatched with condoms and "advice literature" to the woman's home address.

Tracey Forsyth, BPAS lead contraception nurse, said: "Sometimes women worry that requesting the pill in advance makes it look like you are planning on taking chances. In fact, the opposite is true - making sure you have a back-up to help prevent an unwanted pregnancy is making sure nothing is left to chance."

A spokeswoman for pro-life charity Life, Michaela Aston, said there was no evidence the morning-after pill reduced unintended pregnancy rates.

She said: "In fact, if a woman has the morning-after pill at home 'just in case' she may be more likely to engage in risky sexual behaviour than she would normally - particularly over the festive period with the associated increase in alcohol consumption."