The export of military and security services could face tighter regulation following the publication of a green paper by the Foreign Office on Tuesday.

The paper, "Private Military Companies: Options for Regulation", comes after a recommendation made in 1999 by the foreign affairs select committee into the events in Sierra Leone.

The MPs investigated the sale of arms to the country in 1997, for use by then-president Kabbah despite a UK arms embargo. The role of the controversial company Sandline in the West African country also came in for intense scrutiny.

"There is a very plausible argument that private military companies are nothing more than mercenaries and arms-mongers, and that the last thing which a country like Sierra Leone - or any other trouble-spot - needs is the involvement of people like them...At present, there is no legislative prohibition or regulation which deals with private military companies," the committee warned.

The MPs also called for a green paper outlining legislative options for the control of private military companies to be published by August 2000, leaving the publication of the new document 18 months later than the committee had wanted.

However, possible solutions set out by the government include legislation against recruitment for military activity abroad or the action itself, licences for either those companies wishing to buy military or security services abroad, or for those private military or security companies.

Self-regulation of the industry has not been ruled out by the government.

"Today's world is a far cry from the 1960s when private military activity usually meant mercenaries of the rather unsavoury kind involved in post colonial or neo-colonial conflicts. Such people still exist; and some of them may be present at the lower end of the spectrum of private military companies," said foreign secretary Jack Straw.

"One of the reasons for considering the option of a licensing regime is that it may be desirable to distinguish between reputable and disreputable private sector operators, to encourage and support the former while, as far as possible, eliminating the latter," he added.