The Australian Communications Authority today warned mobile phone users not to rely on text messages in an emergency, a warning echoed in UK by emergency services and Oftel.

Despite recent rescues cued by text messages, UK emergency services have warned against relying on mobile phones in life-threatening situations, because of unreliable networks and friends.

In February last year backpacker Rebecca Fyfe and 10 others were rescued from a sinking boat in Indonesia after she sent an SOS text to her boyfriend in England, who alerted UK coastguards, who in turn contacted Indonesian rescue services.

"This was a one-off, but we certainly wouldn't recommend [texting] to contact emergency services," said Bill Smith, senior operations manager at the Maritime and Coastguard Agency.

There are also serious problems from a maritime point of view, according to Smith, with locating a mobile phone's point of origin. If a location is not given in the text, then the best the coastguard can do is contact the telecommunications agency to determine a rough transmission area.

"In a non-urban environment this can be as large as 10km, which gives us a lot of area to cover," added Smith.

Telecomms watchdog Oftel agreed that SMS (short message service) messages do not offer users the same assurance as a phone call.

"Messages can be held up, networks can be busy and the sender never really knows whether the message has got to its destination," said a spokesperson at Oftel.

But there have been the odd situations where SMS messages have saved lives.

"There are situations where SMS messages have been extremely useful, but this doesn't mean people should rely on them," said Andy Simpson at the Mountain Rescue council.

"If mobile phones have signal then people should use them to call, but in many cases when they're most needed they have no signal or the battery will be dead," he said.

The Mountain Rescue council have used SMS messages in one situation to contact a man stuck in a cave. After the alarm was raised, they tried to reach him on his mobile phone but could not, so instead sent him a text message to come out of the cave so the helicopter could locate him.

"He was lucky [the message] got to him, but if it hadn't we may not have known until it was too late," said Simpson.

Another criticism of SMS messages is that they are not 'real-time'.

"They are not instantaneous and they are not reliable and we wouldn't recommend using them," said the Maritime and Coastguard Agency's Smith. "But if it's all the victim has then for heavens sake try it."