Police have sent dozens of letters to anti-cuts activists as young as 17 warning them of the consequences of attending a student demonstration planned in central London on Wednesday.

The letters, which activists say have had a severe chilling effect on protest, have been sent to anyone arrested with previous public disorder offences even if they were later cleared or charges were dropped.

At a briefing Met officials said that letters would only be sent to those who had been convicted of offences but a spokesperson from the Met later admitted this was incorrect and confirmed that anyone who had been arrested in the last year in relation to an "austerity related" protest had been sent the warning.

The single page letter, which arrived through letter boxes on Tuesday, reads: "It is in the public and your own interest that you do not involve yourself in any type of criminal or antisocial behaviour. We have a responsibility to deliver a safe protest which protects residents, tourists, commuters, protesters and the wider community. Should you do so we will at the earliest opportunity arrest and place you before the court."