War on Want, the international anti-poverty charity, yesterday urged the government to regulate British mercenary companies in an attempt to curb alleged human rights abuses against civilians in Iraq and Afghanistan.

Ruth Tanner, the organisation's campaigns officer, told a special meeting in Edinburgh that MPs in the UK had failed to control the controversial private security firm market, despite publication almost six years ago of a green paper outlining possible legal restraints.

"Mounting human rights abuses by mercenary firms making a financial killing from the conflicts are fuelling demands for legislation. But while even the US and Iraqi governments move towards controls, UK ministers take no action," she said.

"It is high time Britain stopped stalling and followed suit with strong measures to rein in these private armies."

The "Big Six" UK companies in the field are Edinburgh Risk Security Management, Control Risks Group, ArmorGroup, the Kroll Security Group, Erinys Iraq and Aegis Defence Services.

Iraq has revitalised the mercenary profession since 2003 and turned it into a multi-billion pound global industry.

UK private security firms saw profits increase from £320m five years ago to £1.8bn in 2004.

The UK government has, meanwhile, spent £179m on private contracts in Iraq between 2003 and 2008 and another £46m in Afghanistan.

At least 44 British private security employees have been killed so far.

The estimated 21,000 British mercenaries operating in Iraq outnumber British service personnel by four to one.

War on Want says guards from British firms ArmorGroup - chaired by Sir Malcolm Rifkind - and Aegis have been involved in shootings.

Mercenaries working for Erinys wounded three Iraqis near the northern city of Kirkuk in October last year, while Aegis employees were shown in an internet video apparently firing randomly at passing civilian traffic during a convoy run to Baghdad airport.

There are 17 UK-run mercenary firms in Afghanistan among the 60 private companies operating there.