Police have reported a large rise in the number of sex offences against minors but they admit they are having trouble making the cases stick in court.

Since the introduction of laws in 1999 requiring people in positions of trust to report suspected cases of abuse, reported cases of sexual assault have shot up.

Inspector Tracy Adams, who heads the Juvenile and Domestic Crime Unit, said: "The legislation has played on people's conscience, knowing they have to do the right thing so they report them.

"It's made the public more aware that there's a lot of it out there and the extent of it is probably greater than what most people believe.

"But it's easier for families to ignore the problem rather than address it."

His colleague WPC Marlo Santiago reminded the public that whistle blowers would not be identified.

She said: "The law is there for people to use it and there is protection for those that report these matters."

Inspector Adams said that some members of the public were still reluctant to help in the prosecution of the sex abusers unless they had been directly affected by the crime.

He said: "When it doesn't affect the family then you still get the notion of `It's none of my business' and you won't get too much assistance."

He said the rise in cases was creating a lot of work for his four-woman and two- man team based on Reid Street.

He said: "There's been an increase due to mandatory reporting, we're having to deal with more and more cases, which is a strain on our resources.

"We find a lot of times these offences have been happening for years. It's almost like going back to cold cases it can prove difficult to get evidence.

"The Department of Public Prosecutions decides if there's sufficient evidence for a case. If there's not enough evidence to pursue it we still try to get counselling and other agencies involved so the victim gets the help they need."

He said only around 50 percent of reported cases go to court.

"There's new legislation saying corroboration is no longer required but we still find it. You can't just go on one person's word, you need other supporting evidence but it could have happened months or years ago.

"Finding that additional evidence so you feel you will secure the conviction is difficult.

"When children are of tender years they can't swear on oath therefore there must be corroboration.

"There's no real way around it, that's the legislation we have to work with. It's disappointing when you believe they are a victim of a serious crime but you know the court won't find enough evidence to get the conviction."

He admitted there were sometimes delays in getting cases to court.

"Sometimes you have to wait for DNA evidence to come back or you are waiting to hear from the DPP's but in some cases it has gone to court within a week.

"Sometimes when you rush to get things in court you can overlook crucial things."