In one unprecedented case, all 60 families granted places at Ecclesall Infant School were asked to individually prove they lived where they said they did, following controversy when some children living in the catchment were turned away.

Protesting parents claimed some families were successfully making fraudulent applications - but all 60 addresses checked out.

Nationally cases of parents lying to get into leading schools are on the increase, with one authority reporting the number of cases up from five to 50 over the course of a single year.

But in Sheffield the number of cases has remained relatively constant, despite increasing pressure on places in the primary sector - around 150 children being turned away from all three of their selected schools for 2008/9.

So far this academic year five cases have been investigated, following anonymous tip-offs and information from schools that addresses did not match previous records.

But only two of those were proven, and in both cases the places at High Storrs and Tapton schools in the south west of the city were withdrawn.

"A problem in these cases is that there is no effective penalty if parents are caught out, other than the loss of a school place which was not theirs to begin with," said John Bigley, access manager at the the city council's children and young people's service.

"If that is the only sanction for people who get caught, what have they got to lose by making a false application?

"Our message to parents is, if you think someone is misusing the system, then tell us and we will investigate, anonymously if necessary.

We want to catch the cheats as much as anyone," Mr Bigley said.

Admissions officers say many parents believe the extent of fraud is more serious than it is, with rumours and anecdotes often taking the place of hard fact.

Some argue that the number of families caught out is just the tip of the iceberg, and that admissions procedures are routinely flouted.

But Mr Bigley points out that schools now have detailed data bases and that addresses can often be checked using individual pupil histories, with that information also stored centrally.

"All parents give schools contact details in case of emergencies and it would be a strange parent indeed who gave false information in those circumstances," he said.

"But we can't carry out thousands of routine checks on a city-wide basis, it would not be a good use of our resources and no other council does it. There are 5,500 secondary places allocated in a year alone."

It also rankles with some that if parents are caught out once a child has started school, often the youngster is allowed to keep his or her place.

"If that happens the key factor is how long the child has been settled at the school - we are not going to hurt the kid in such circumstances," Mr Bigley added.