Soaring premiums since September 11 have led many of the world’s biggest companies to choose to cover their largest risks themselves, according to leading broker Aon.

Self-insurance through captive companies has been around since the 1970s, but Aon says there’s been a jump in the amount of risk being kept in captives by multinational companies intent on avoiding high premiums.

Aon Captive Services Group CEO Stephen Cross said in London that Aon has seen a jump of around $US8.1 billion in gross premiums written by the captives it manages from 2002 to last year.

Mr Cross says though the cost of cover charged by insurers has started to fall, insurers continue to exclude many risks from policies since the September 11 attacks, which costs insurers around $US45 billion.