Majorca has announced plans to monitor British mobile phones this summer. The surveillance tactic is part of a new strategy to combat overtourism, amid growing anger from locals on the largest Balearic Island.

Opposition parties have criticised the plans, which will use the number of phones to measure beach overcrowding. They agree that the problem of mass tourism has to be dealt with but claim the beach monitoring proposal will not solve the crisis.

The plan will cover popular tourist spots…