Government-owned institutions are becoming big drivers of sustainable investing -- or buying firms which are socially and environmentally responsible, or sectors which tackle climate change or resource scarcity.

Norway's $400-billion-plus sovereign wealth fund, which is the world's second largest, is a big advocate of "green" investing, naming and shaming companies which do not fit the investment guidelines set by the government.

The guidelines rule out holding investments in certain firms,  for instance those that produce nuclear arms or cluster munitions, or that damage the environment or abuse human rights.

It has just expelled Israel's Elbit Systems for supplying surveillance equipment for the West Bank separation barrier.

RCM, equity-management arm of Allianz Global Investors, says that sustainable investment is gaining momentum and offers investors a unique diversifier.