The taoiseach insisted in the Dail last week that any sex offender coming from Northern Ireland or Britain was obliged by law to notify gardai of his or her whereabouts and, he said, failure to do so carries a penalty or imprisonment. That this is a fact is irrefutable but there's no guarantee that sex offenders will do so. All the evidence points to the contrary.

Last week a popular DJ in Donegal was revealed to be a convicted child rapist called Alexander Colin Dalgleish, named as one of Britain's five most-wanted paedophiles. He vanished from Donegal before he was identified and is still on the run. He had failed to tell the garda authorities about his past.

He is just one of a number of dangerous men convicted of despicable crimes in other jurisdictions and believed to be living in Ireland.

They make a mockery of Ahern's certainty.

That list of paedophiles includes Raymond Hewlett, who was jailed for a series of sex attacks on children in England and last known to be in Kinsale, Co Cork before he went missing.

It also includes Tony Knowles, who numbers an 18-month-old baby among his victims. He disappeared while on bail here last year.

Michael Rowley, Joshua Karney and Roger Gardener, all convicted of underage sex crimes, are also believed to be in Ireland . . .

whereabouts unknown.

The problem is that the sex offenders' register, established in 2001, relies on the goodwill of offenders to sign on. They are supposed to inform gardai of any change of address but there are no restrictions to prevent them hanging around schools, parks or playgrounds.

In fact, to call it a sex offenders' register at all is erroneous. It is cold comfort to parents that the onus is on perverted, highly manipulative individuals to show such civic spirit.