Talking or texting on a mobile phone while driving is as dangerous as drink driving, a new study suggests.

Currently in Ireland, the legal blood alcohol limit is 50mg per 100ml (0.5mg/ml) of blood for experienced drivers and the use of mobile phones while driving is illegal. However, many people continue to drive over the limit and use their phones regardless.

Spanish and Australian scientists decided to compare the effects of driving while using a mobile phone with driving while over the limit. Their study involved 12 healthy people who volunteered to take part in a driving simulation test. All had a full driving licence. They were tested for two days, each day a week apart.

The first day involved them taking part in the driving simulation test after they had consumed alcohol. Their objective was to hold their position in the centre of the left lane on the screen in front of them at a speed of between 60 and 80km/h. If a lorry appeared on the screen, they had to brake.

The second day involved various scenarios with a mobile phone - from having a normal, free flowing conversation to having a more cognitively demanding conversation. This included the participants being asked a question like ‘how many of your friends' names begin with a vowel?'

Texting was also included.

The scientists compared the blood alcohol levels with the effects of using a mobile phone and found that if the phone conversation was cognitively demanding or if the person was answering a text, the results were comparable to being over the alcohol limit.

A microphone and headphones were used to simulate a hands-free effect.

According to the findings, when the conversation using the hands-free equipment was simple, the effects were comparable to a blood alcohol level of 0.04 mg/ml, which is below the legal limit of 0.5 mg/ml in countries like Ireland, Spain and Australia.

"However, when more attention was required, their alcohol level analogue shot up to 0.7 mg/ml, which is above the legal limit in these countries yet below in other countries, like the USA or the UK, where up to 0.8 mg/ml is allowed," the scientists noted.

They believe that the results indicate that ‘the use of hands-free devices could also put drivers at risk'.

Meanwhile, the scientists also found that when answering text messages, ‘the rate stood at 1mg/ml, which is illegal in all of these countries'.

Up until the end of 2011, the legal blood alcohol level in Ireland was 80mg per 100ml. However, this was reduced to 50mg per 100 ml for experienced drivers and to 20mg per 100ml for learner and professional drivers.

Holding a mobile phone while driving has been illegal since 2006, however, the use of hands-free kits is permitted.

Details of these findings are published in the journal, Traffic Injury Prevention.