Almost all the Islamic bonds sold by companies in the Gulf region do not entirely conform to the religion's law, according to an Islamic finance industry body, casting doubt over the legitimacy of a multi-billion dollar market that is growing rapidly.

Islamic bonds, or sukuks, are structured in a similar way to conventional bonds, but offer coupon profits instead of coupon interest, as interest is banned under Islamic law. Nearly $40bn (€27.3bn) of these bonds have been issued this year, from virtually nothing in 2001.