Allegations of rape and sexual assault in the armed forces should always be investigated by civilian police rather than their military counterparts, campaigners have said.
Human rights campaign group Liberty said the "deeply-flawed" military justice system was not equipped to investigate allegations of serious abuse and criminality, and lacked the safeguards to ensure independent and impartial investigations, in turn allowing harassment and abuse to go unchecked.
The groups' new report, Military Justice: Proposals for a Fair and Independent Military Justice System, has made several recommendations, including the suggestion that crimes like rape and sexual assault in the armed forces are always investigated by local rather than service police.
Its authors suggested that because service police worked closely with personnel on base, there was a high chance they would know the alleged victim or perpetrator, potentially undermining their ability to investigate impartially.
The group claimed the lack of independence was worse when either alleged victim or perpetrator was a member of the relevant service police, giving the case of Anne-Marie Ellement - who committed suicide in an Army barracks two years after alleging she had been raped by two colleagues - as an example.
Liberty also called for decisions about whether to investigate allegations of sexual assault, exposure and voyeurism to be taken out of the hands of commanding officers, saying they lacked the training and expertise to deal with complaints of sexual assault.
The group's policy officer Sara Ogilvie said: "Our deeply-flawed military justice system is not equipped to investigate allegations of serious abuse and criminality - we must stop failing those willing to risk their lives for our country.
"Our forces can only be strengthened by increased fairness and oversight.
"British troops are sent to defend rights around the world - it's time their own were properly protected."
The report contained six recommendations, including that a nonymised statistics on the number of allegations of sexual assault and rape made by or against a member of the armed forces should be collected and published, and that Parliament should amend the Armed Forces Act so that sexual assault, exposure and voyeurism have to be referred to the police, taking the decision out of the hands of commanding officers.
It also recommended that r ape and sexual assault were added to the category of Very Serious Crimes which must always be investigated by local police forces rather than service police forces, and that a rrangements for investigating serious crimes committed abroad should be changed so an independent police force rather than the service force was responsible.
The three service police forces should be brought within the civilian system of police oversight, the report also recommended, as well as suggesting that the Armed Forces Ombudsman should be given powers to investigate the merits of a complaint as well as claims of maladministration.
The report comes after n ew legislation to change the way complaints are dealt with in the armed forces was hailed last month as delivering "real change" for personnel.
The Service Complaints and Financial Assistance Bill, unveiled in the Queen's Speech, will see the creation of the armed forces' first Service Complaints Ombudsman, with strengthened powers designed to ensure complaints are dealt with properly.
The provisions, which are hoped to improve the efficiency of the system and ensure the armed forces are held to account, come after past concerns that too many complaints, including allegations of bullying, were delayed or not dealt with properly.
In March, the Service Complaints Commissioner (SCC) Susan Atkins found the current system was failing and called for a new ombudsman to be set up without delay.
Under the new Bill, the SCC's role - a post which came into effect in January 2008 following the Armed Forces Act 2006 - will become an ombudsman with increased powers, including the ability to investigate whether a complaint has been handled properly; the power to recommend action to the Defence Council, and the power to overturn a decision by the chain of command to exclude a complaint.
The SCC has not previously had any legal powers in relation to individual complaints, and there have previously been concerns within the armed forces that an outside regulator was incompatible with the chain of command.