The whooping cough outbreak has now claimed the lives of 10 babies, say health officials.

The Health Protection Agency (HPA) said September alone saw 1,322 confirmed cases in England and Wales - 300 more than the total figure for the whole of 2011.

So far this year in England, the infectious disease has resulted in the deaths of 10 babies under the age of three months, with the total number of confirmed cases for the first nine months of 2012 standing at 6,121.

In a bid to combat the outbreak - the biggest for 20 years - chief medical officer Professor Dame Sally Davies, the government’s principal medical adviser, has said that all pregnant women in the UK and aged between 28 and 38 would now be offered a whooping cough vaccination to protect their unborn babies.

A large increase in the number of cases is causing concern in the Northwest, where there have been 308 cases so far this year compared to just 73 in 2011.

The number is more than five times higher than the annual total reported last year and almost seven times higher than 2008 – the last ‘peak’ year before this current outbreak.

Last month, the Department of Health announced pregnant women would be offered whooping cough vaccination to protect their newborn babies, not usually vaccinated until between two and four months.

The HPA says the introduction of the vaccine programme in pregnant women will help to boost the short-term immunity passed on by women to their babies while they are still in the womb.

Dr Mary Ramsay, head of immunisation at the HPA, said: “We have been very concerned about the continuing increase in whooping cough cases and related deaths and welcome the urgent action recently taken by the Department of Health to introduce a vaccine for pregnant women.

“The introduction of a vaccine for pregnant women will not have an immediate impact on serious infection in infants so vigilance remains important. Working with the Department of Health we will continue to regularly monitor figures to evaluate the success of the programme.

“All parents should ensure their children are vaccinated against whooping cough on time, even babies of women who’ve had the vaccine in pregnancy – this is to continue their baby’s protection through childhood.”

She said parents should also be alert to the signs and symptoms of whooping cough – which include severe coughing fits accompanied by the characteristic “whoop” sound in young children but as a prolonged cough in older children or adults. It is also advisable to keep babies away from older siblings or adults who have the infection.

Whooping cough, also known as pertussis, affects all ages. Young infants are at highest risk of severe complications and death from whooping cough as babies do not complete vaccination until they are around four months old.