The Metropolitan police have said organisers of this weekend’s Unite the Kingdom and March for Palestine demonstrations will be held responsible for any hate speech connected with the events, in what they expect to be “one of the busiest days for policing in London in recent years”.

Tens of thousands of people are expected to march in the capital for the Unite the Kingdom event in central London and the Nakba: 78 March for Palestine from south Kensington to central London. Senior officers said protesters would face “the highest degree of control”. The FA Cup final is also due to be held at Wembley on Saturday.

In a briefing, James Harman, a deputy assistant commissioner, said a “zero tolerance” operation of “unprecedented” scale would include 4,000 officers, at a cost of £4.5m, and “swift and decisive” action against disorder and hate speech.

Live facial recognition will be used in an area of Camden where Unite the Kingdom attenders are expected to gather outside the event itself, “comparing the faces of…