Abu Dhabi Investment Authority, the world's largest sovereign wealth fund, has hired Burson-Marsteller, the US public relations company, to handle its communications amid rising scrutiny of petrodollar flows into western economies.

The secretive fund, which recently invested $7.5bn (€5.1bn, £3.8bn) in Citigroup, has so far largely refused to engage with the public, declining to comment on deals, and preferring to communicate solely with its network of leading banks and funds.