KABUL (Reuters) - A United Nations sponsored report has found that Afghanistan government officials who headed oversight of the police suppressed complaints of corruption against the force and has recommended their dismissal, according to a copy of the document seen by Reuters.

The United Nations Development Programme is also investigating why its own division, the Law and Order Trust Fund of Afghanistan (LOTFA), which commissioned the report, did not show it to senior U.N. officials after it was submitted in January.

It is the latest in a series of questions about LOTFA, which has received around $3.6 billion from international donors since 2002 to pay Afghan police force salaries and other expenses.

LOTFA commissioned the report late last year to find out why the main system for filing complaints about police misconduct, a 24-hour phone line, rarely led to prosecutions.

It found that only nine out of more than 2,000 complaints referred to the inspector general’s office in the Afghan interior ministry over a year were forwarded for prosecution. It concluded the chief of the agency, Hakim Nejrabi, and his senior staff were ignoring or blocking complaints.

"Systemic corruption is endemic to the organization because the leadership has not only tolerated corruption, they have facilitated it and, in many instances, participated in it," the report said, recommending the removal of Nejrabi and all of his senior staff.

Nejrabi denied all allegations made in the report, calling the findings "a political character assassination". He said more than 50 interior ministry officials had been investigated since he took office 13 months ago, and 22 cases had been forwarded for prosecution.

The UNDP said it learned of the report only when Reuters asked about it earlier this month and is now conducting a review of internal processes "to improve efficiency, oversight and accountability to prevent this from happening again."

It also said a copy was then immediately provided to Afghanistan’s anti-corruption body, the Independent Joint Monitoring and Evaluation Committee (MEC). Officials at the committee confirmed they had received the report.

UNDP did not say why submission of the report was delayed and LOTFA's manager, Basil Massey, declined to comment.

Last year, the U.S. special inspector general for Afghanistan reconstruction criticized LOTFA for allegedly losing track of millions of dollars in payments to ghost employees. In 2012, it was investigated for procurement fraud.

Yama Torabi, a member of the MEC, said the report "shows that for years they've done nothing to solve the problem - not LOTFA, the Afghan government, or previous ministers."

(Editing by Paritosh Bansal and Raju Gopalakrishnan)