HOSPITAL chiefs today pledged to step up maternity ward safety after admitting that a problem with their alarm system meant it failed to go off when a security-tagged baby was taken out of the building.

The revelation came after an inquiry into the case of newborn Carla Roberts, whose security tag failed to set off the alarm when she was taken out of Queens Park Hospital by her parents.

Dad John Roberts only noticed the tag -- which should have been removed by a hospital midwife -- when they returned home to the Shadsworth area of Blackburn.

After more than a week of tests on the system, which operates on a magnetic loop triggered by the tags, operations director at the hospital John Dell said the fault was down to a lapse in the magnetic field.

And bosses are now hoping to install a second loop to provide extra back-up for the system.

Despite the incident the system still has the full backing off hospital bosses and the Community Health Council.

"We accept that these things cannot be 100 per cent. It is a magnetic field and it is possible that you can get dips," said Mr Dell. "It seems it would not operate at the time of a dip in the loop which is what may have happened and is obviously a concern."

Mr Dell added that to stop any repeats of this incident the hospital was looking to back up the £30,000 alarm system and had been in consultation with the alarm company Cotag.

"We are looking at installing a second loop in the system so that if there was a dip in one part of the original system the second one would back it up. It would be very coincidental if both suffered dips."

Cotag was called in for two days and "virtually every tag" was put through the series a number of times -- including the one retrieved from John Roberts.

"We still have every confidence in the system, installing another loop is a back-up to our back-up," said Mr Dell. "We want to assure parents that there are other systems in place and our staff are extremely vigilant. All doors to the ward are locked and cameras are in place which are continuously monitored. What we want to do now is make it fool proof." The costs of installing a further loop are still to be confirmed although Mr Dell said money was not the concern.

"We are not sure of the costs." he said. "But this is about the safety of babies. They come first."

Chief Officer of the Blackburn, Ribble Valley and Hyndburn Community Health Council Nigel Robinson said he was satisfied with the present system.

"The hospital and the trust have dealt with this quite thoroughly and no system is fool proof. We have investigated what went wrong and we can't really answer that but we are going to take steps to make it better with the extra loops," he said. "I am reassured that the hospital has taken this seriously and I am happy with the system."

Mr Roberts said he still had confidence in the hospital. He said: "Up until then I thought the security was very tight and putting extra loops in can only be a good thing."