Complaints to regulators have soared over the last year as advertisers directly target mobile phone users.

Increasingly, such unsolicited texts dupe people into phoning premium rate numbers. One method is to send a romantic message from an mystery admirer.

Premium rate calls watchdog Icstis has received more than 150 complaints in the past nine months about unsolicited messages.

Wireless confusion

The Advertising Standards Authority has also seen a rise in problems and has upheld six complaints about text message promotions this year, compared with none the previous year.

Text messaging is a double-edged sword. It can ruin your brand if you misuse it or be deadly effective in creating customer loyalty if used correctly

Pamir Gelenbe, FlyTXT

"It is an issue we have been concerned about for quite a while," said a spokesman for the Consumers' Association.

"Increasingly people are giving out their mobile phone numbers and there doesn't seem to be sufficient control on where those numbers end up. People are also confused about who to complain to," he said.

For marketers, SMS can prove an invaluable route to customers. Research firm Forrester predicts that 56% of firms will use text messaging as a marketing tool by 2003.

But unwary mobile users who reply to a suprise message like this one - "I've always liked U. It's time to come clean" - could find themselves paying 165 pence or more.

Mobile spam

SMS marketing company FlyTXT takes the view that if certain key rules are adhered to it can be beneficial to both consumers and firms.

"Text messaging is a double-edged sword. It can ruin your brand if you misuse it or be deadly effective in creating customer loyalty if used correctly," Director of Development at FlyTXT Pamir Gelenbe told BBC News Online.

Tighter regulation is necessary so that users can regain control over what they get on their phones

Spokesman, Consumers' Association

Responsible SMS marketing must involve a two-way relationship between advertiser and customer, ensuring that all recipients have opted-in to receive messages and allowing them to opt-out at any time, said Mr Gelenbe.

He disagrees that mobile spam is a huge problem.

"In reality, there isn't a lot of spam over the air because marketers have to pay between 5p and 10p for each message and unless you get a decent response rate you would go bankrupt," he said.

In Japan, where recipients rather than senders are charged for messages, spam is a much bigger problem with nine out of every 10 messages on the DoCoMo network estimated to be spam.

Tighter regulation

Orange urges users of its network to contact its customer service lines if an unsolicited text message is received.

Who to complain to

In first instance your network operator Icstis is official regulator for premium rate services Oftel in the last resort can take action against rogue companies The Mobile Marketing Association may also be worth a call

"If the message has been generated using a number on the Orange UK network we can bar the subscription or block the ability to send text messages from that number," reads a statement from the company.

If the text message has been generated using a number on another network, Orange can either bar the sender number from sending SMS to Orange customers or block the message centre concerned.

Spam generated overseas is harder to control but Orange says it is "taking measures" to deal with it and is also working on software that would block spam.

At a government level the European Union has passed a law forcing marketers to get explicit permission from customers before sending e-mails or text messages for advertising purposes.

The law should be adopted in member states, including the UK, by the summer of next year.

Action needs to be taken as soon as possible, said the spokesman for the Consumers' Association, himself a victim of airwave spammers.

"Tighter regulation is necessary so that users can regain control over what they get on their phones," he said.