Security experts have slammed applications used to spy on mobile phone users.

The warning from researchers at F-Secure comes as a growing number of programs are being launched to track and record mobile phone conversations and text messages.

Such software is chiefly marketed at those who suspect a partner of having an affair, or to monitor children's telephone activity.

F-Secure experts claim that, far from providing security, this type of software could allow anyone to access the information collected.

For example, they demonstrated to vnunet.com that it possible to find call times, numbers dialled and SMS messages from users of Mobile Spy software.

"They are not building this stuff to make people secure, they are building it to make money," said Sean Sullivan, a senior researcher at F-Secure.

"It would be easy to build a software tool that could automatically scan and record the information from anyone who had ever used the service."

Mobile Spy states on its website: "By purchasing from an established company that has been creating spy software products since early 2003, you can rest assured you will receive professional grade software and service.

"With Mobile Spy there is no need to trust an offshore company with your confidential data."

F-Secure designates such software as 'malware', since the code can run without the user's knowledge. Legal authorities in Britain have also stated that the Flexispy application from Flexispy.com may well be illegal.

Symbian, however, has defended such software's use, maintaining that it has legitimate applications.