An alleged paedophile avoided conviction after a child he was accused of molesting forgot the exact dates of offences, it emerged yesterday.

A legal loophole meant the man, charged with a string of assaults, walked free from court on a technicality.

A jury at Derby Crown Court were directed to find the 31-year-old not guilty after the girl - who was six at the time of the alleged offences - could not remember if they happened before or after May 1, 2004.

The date was vital because it was then that the new Sexual Offences Act 2003 came into force.

Sex offences committed after May 1, 2004, are dealt with under that legislation, but those before are still prosecuted under the older 1956 act.

If it cannot be established under which act to prosecute, no charges can be brought, said the Crown Prosecution Service. In police interviews, the girl gave specific dates so the man could be prosecuted using the correct legislation.

He was charged with two counts of indecency with a child under the 1956 act and, under the new laws, two counts of oral rape of a child aged under 13 and one count of causing or inciting a child under 13 to engage in sexual activity.

Under cross-examination, however, the girl could not give accurate dates.

Defence counsel said the Crown could not prove the case if it could not establish whether the offences happened before or after May 1, 2004.

"Cases have had to be withdrawn from the jury up and down the country because of this," said barrister Caroline Bradley.

Judge David Price directed the jury to deliver not guilty verdicts because "you can't say whether this alleged abuse occurred under the old act or the new act".

A Crown Prosecution Service spokesman said: "These cases are extremely rare and only occur where a victim is unsure of either, the specific date, or the general period in which the incident occurred."