Technology that tracks customers as they navigate shopping centres by picking up signals from their mobile phones has come under fire from civil rights campaigners and consumers.

The system means centres can analyse data such as how long visitors stay, where their favourite spots are and their preferred routes as they move around a mall. Shopping centres argue the system benefits both customers and retailers and insist privacy is not compromised because individuals are not identified.

But campaigners are claiming it is wrong that shoppers have no choice but to be monitored. Nick Pickles, of the campaign group Big Brother Watch, said: "The only way to opt out is to turn your mobile phone off. You're not asked if you want to take part, you're not asked if you want to opt out."

Pickles said he was pleased that customers remained anonymous. But he added: "It is assumed that the shopping centre has the automatic right to track people's mobile phones – to me that's wrong."

Under the FootPath scheme a series of monitoring devices are installed throughout a shopping centre. The units pick up signals from a customer's mobile phone and can pinpoint the person's position to within 2m. The data gleaned is fed to a processing centre where it is collected, analysed and fed back.

According to Path Intelligence, the Hampshire-based company behind FootPath, the information can help centres understand what mix of shops works best, how promotions affect the number of customers and can optimise rents by finding out which spots are the most profitable. It can also give an insight into where facilities such as food-courts or toilets are best sited and can help plan for emergencies.

It says its detector units do not allow it to obtain telephone numbers, listen to calls, read messages or identify the user. Path Intelligence says it has consulted with the information commissioner to make sure that privacy is not infringed.

However the company refused to say how many shopping centres in the UK used the technology or identify any of those that had installed it. The company only said that it was used in seven countries.

One of the centres that does use the system is Princesshay in Exeter, where small signs read: "To improve out customer service we monitor the use of mobile phones to help show us how this centre is used by its customers. No personal data is stored at any time."

But shoppers were not impressed. Dave Jones, who was looking for a bargain in the sales, said: "It feels like an invasion of privacy whatever they say about it being anonymous. I don't like the idea of anyone being able to pick up my mobile phone signal as I go about my business. If feels a bit creepy."

Wayne Pearce, the director of the centre, said: "The anonymous data we receive each week allows us to monitor footfall, dwell time and the way in which shoppers use the centre. This is turn helps us make decisions on improving the mix of retailers, providing better service by deploying greater numbers of staff to meet shoppers needs and helping avoids bottlenecks by improving the safety and layout."

Gus Hosein, the executive director of Privacy International, said: "Simply notifying people that their every move is being tracked does not absolve Path Intelligence or the shopping centres that install their technology. Until a proper opt-out is introduced, this technology will be a serious threat to personal privacy."