Two tags at the hospital were faulty

One tag failed to activate the maternity unit's alarm system at Prince Charles Hospital in Merthyr Tydfil, and a baby was taken home still wearing it.

A number of hospitals in Wales now tag babies as soon as they are born to prevent them from being snatched.

The extra security was part of a UK-wide review in the 1990s prompted by the abduction of Alex Griffiths more than 10 years ago.

Alex was 36 hours old when she was snatched by bogus health worker Janet Griffiths (no relation) from St Thomas' Hospital in south London in January 1990.

It was 17 days before police found the baby in a cottage in the Cotswolds.

As part of the overhaul of policies on access to maternity units, Prince Charles Hospital opted to tag infants.

This way, any passing through the security system would set of an alarm which would automatically spur staff into action.

But now it has emerged that one baby born on the site was accidentally discharged and taken home still wearing the tag.

It had failed to activate the alarm as the baby was taken through the security system.

A check was carried out on all the tags used at the hospital and two were found to be faulty.

The hospital is now upgrading the system to make sure that if an alarm goes off security staff and porters are alerted immediately.