Updated

GENEVA -- Major private security companies signed a code of conduct Tuesday, pledging to respect human rights and the rule of law in conflict zones such as Iraq and Afghanistan, where some have been accused of abuses against the local population and reckless behavior.

The voluntary code developed by industry and government representatives was signed by 58 companies including Britain's G4S and U.S.-based DynCorp International and Xe Services -- formerly known as Blackwater Worldwide.

"This initiative has the potential to address gaps in oversight and accountability," said U.S. State Department legal adviser Harold Koh.

Private security companies contracted by governments and non-governmental organizations have seen a boom in business over the past decades, particularly due to the wars in Iraq and Afghanistan, where they have been hired to guard individuals, installations and convoys.

However, in both countries companies have faced accusations of wrongdoing. In one incident Blackwater guards faced criminal charges for a 2007 incident in which 17 Iraqi civilians were killed.

Devon Chaffee, a lawyer for the group Human Rights First, said the signing of the code was "an important first step" but that an effective monitoring mechanism still needs to be agreed.

She also urged governments not to take the code as an excuse to refrain from establishing proper laws regulating the conduct of private security companies and punishing those found guilty of abuses.

The new code requires companies to ensure their employees "take all necessary steps to avoid the use of force" and forbids mistreatment of detainees, sexual exploitation and forced labor.

Companies who fail to live up to the code may find themselves in breach of their commercial contracts and will be flagged up to potential clients.

Andrew Clapham, professor of international law at the Geneva Graduate Institute, said the code was "certainly not a fig leaf."

"There's a lot of money in this industry and this code is going to be vital to it," Clapham said.

His words were echoed by Nick Buckles, the head of G4S, which is the world's biggest private security company with has an annual revenue last year of $11 billion and 600,000 staff.

Buckles said he hoped governments would make compliance with the code a "critical factor" in deciding which companies to hire.

"We believe this, more than anything else, will help drive up standards," he said.