Tom Harris, of Alver Road, Gosport, pictured above, and a 17-year-old girl from Fareham, were arrested at Halloween last year for failing to give their names and addresses to a constable as they took part in a demonstration outside the controversial animal testing Wickham Labs, in Wickham, near Fareham.

The prosecution has now come under fire for being a massive waste of taxpayers cash and police time.

The police are entitled to demand a person's name and address but only if officers believe they are carrying out antisocial behaviour likely to cause harrassment, alarm or distress.

The case at Portsmouth Magistrates Court was dismissed after a day-and-a-half of the planned three-day trial because magistrates said there was insufficient evidence.

An inspector, three sergeants, a police constable, a PCSO, a special constable, and a resident living opposite the labs were all called to give evidence in a bid to prove the case.

No other arrests were made during the evening protest, which included up to eight activists in fancy dress chanting slogans through a megaphone.

Mr Harris, 25, said: 'Justice has been done. It has been an absolute waste of money, it hasn't been in the public interest, and it has been an affront to our right to protest and freedom of assembly.'

He added they were intending to file a civil case against the police.

Inspector Jim Pegler, for Winchester East, said: 'A balance must be struck between the right of people to protest and the rights of the community to enjoy a peaceful existence.

'This protest was taking place at 8pm, 10 metres from residents' homes and officers received reports that young children were being scared and kept awake by protesters wearing masks and using a megaphone.

'Police officers at the protest therefore had reasonable grounds to suspect that anti-social behaviour was taking place, following the complaints from members of the public.'

Cate Clark, spokeswoman for the Crown Prosecution Service, said the case had been reviewed and experienced prosecutors had decided there was 'a realistic prospect of conviction and that it was in the public interest'.

Matthew Sinclair, policy analyst at the TaxPayers' Alliance, said: 'The time of courts, police and prosecutors is expensive and to have taxpayers' money spent to so little effect is deeply disappointing.