More than 300 members of United Nations peacekeeping missions have been investigated by the international body for alleged sexual exploitation and abuse during the past three years.

A senior UN official made the announcement Friday, saying that half of those who were investigated were fired or sent home.

The news came after a report by the U.K.'s Daily Telegraph newspaper, which included allegations that UN personnel in southern Sudan took part in sexual exploitation and abuse of more than 20 children.

The UN was trying to determine whether they were fresh charges, or ones the UN had already investigated as part of its probe, The Associated Press reports.

Jane Holl Lute, the UN's assistant secretary general for peacekeeping, said the organization had stepped up efforts in the past two years to crack down on sex abuse. However, she told a news conference there is still work to be done, noting: "We're not satisfied with where we are."

Lute said that between January 2004 and the end of November 2006, the UN probed allegations of sexual exploitation and abuse involving 319 peacekeeping personnel "in all missions" - from East Timor, the Middle East and Africa to Kosovo and Haiti.

Resulting from the investigation, 18 civilians, 17 international police and 144 military personnel were dismissed, she said.

The UN currently has 16 peacekeeping missions in various corners of the globe. The organization sees a staff turnover of 200,000 people from 100 countries every year, The Associated Press reports.

With that kind of volume, it's inevitable that members "are going to behave badly," Hall Lute told a news conference.

"What's different now is ... our determination to stay with this problem ... and constantly improve our ability to deal with it."

In total, 63 per cent of alleged incidents of misconduct from January to the end of October, 2006, were related to sexual abuse and prostitution, according to AP. One third of those involved prostitution.

The UN first came under close scrutiny in relation to sexual abuses in early 2005 after allegations that peacekeepers in Congo traded food and money for sex with Congolese women and girls.

A report several months later slammed the body's military arm as deeply flawed and claimed abuses had been reported from Bosnia to Kosovo and Cambodia, East Timor, West Africa and Congo.

As a result the organization brought in a new code of conduct and stepped up its zero tolerance policy on sexual abuse.

Efforts are currently underway to combat prostitution.

According to the UN's Department of Peacekeeping, there are 13 investigations currently underway in Sudan, dealing with allegations of sexual exploitation and abuse by members of peacekeeping forces.

Several Bangladeshi peacekeepers have been disciplined for their alleged roles in a case of sexual exploitation and abuse in southern Sudan in June 2006.

With files from The Associated Press/>