A multi-million-pound scheme sold to residents as a way of helping them find a parking space in Westminster will also be used to increase parking fines and ramp up charges in high-demand areas, critics claim.

Hi-tech parking sensors are being launched along with a new smartphone app to help motorists locate empty parking spaces.

They were introduced to St John’s Wood High Street and other locations in Westminster in August, and the council is considering rolling them out borough-wide.

But campaigners claim the town hall is misleading motorists, and say the sensors will be used to alert wardens to motorists overstaying their parking tickets, boosting the number of fines.

Manufacturer Town and City Parking say the system can notify wardens, and advertises it as “enabling effective enforcement”.

Meanwhile, Westminster’s information analyst Lewis Johnson told technology magazine Computer World UK that the sensors can also be used to identify streets with a high demand and turnover of visitors, allowing the council to increase parking charges accordingly.

Parking campaigner Paul Pearson, who runs website penaltychargenotice.co.uk, said: “This is another example of Westminster Council seeking to pull the wool over the eyes of motorists by trumpeting this new technology as a good thing, but neglecting to mention it will be used to enforce and increase charges.

“This is typical Westminster Council. Do they really expect us to believe that they would spend millions assisting motorists?”

A spokesman for Westminster council did not rule out using the sensors for enforcement and increasing charges.

He stressed the scheme was in its early stages and the primary purpose was the free parking app.

Maureen Butterworth, an independent trader on St John’s Wood High Street, said the sensors are a waste of money.

She said: “I have the app, but by the time I get to the parking spot, it’s usually been taken. It doesn’t work and it’s a waste of our business rates.”

Cllr Daniel Astaire, cabinet member for business, said: “This is a truly ground-breaking project.

“Only San Francisco really has anything similar in the world, and even then we are ahead of the curve in developing a live app that links into the system.

“We have worked hard to get this project off the ground, as it will benefit motorists, businesses and residents right across the city.”