Faisal Private Bank's chief executive, Marco Rochat, said the absence of a global set of harmonised rules on Shariah compliance created an uneven playing field.

Some investments are permitted to some investors but not to others, he was quoted as saying.

"We need a body to oversee the market and ensure trading compliance, like you have in traditional banking, or in accountancy. A regulated environment would help a lot of investors," Mr Rochat said.

Shariah law bans interest on loans as well as investment in areas such as gambling. Under modern Islamic finance, a large sukuk bond market, which in some ways resembles Western-style debt financing, has developed and a number of the world’s banks, such as HSBC and Barclays, have developed Shariah finance arms. There continues to be debate on whether some of these modern Shariah products are fully consistent with Islamic law.

Mr Rochat said the market for Shariah-compliant products was still unregulated. That meant there were, at times, large differences between accepted products in the Middle East, North Africa and Malaysia.

"We need to see this period as the beginning of an evolution in this area," Mr Rochat said. Without a broader and more coherent oversight, different markets will continue to treat products in an ambivalent manner, he said.