Increases in insurance premiums on global shipping could be the result of more than just underwriters' decisions to raise war risk insurance charges.

Lloyd's Underwriters' Association (LUA) secretary Neil Smith said the LUA suspected other parties in the shipping chain could also be adding to the overall cost of shipping's increased rates. "That is a suspicion which we are now trying to identify and to sort out exactly what the costs are," he said.

Pakistan is currently one of several countries trying to negotiate lower premiums on shipping with Lloyd's. The country fears economic losses as a result of the increased charges.

A source said Pakistan felt the rate increases were "unjustified" because Pakistan's only port, Karachi, is 1,200 miles away from Afghanistan and unaffected by the current conflict.

However, Smith said the LUA's underwriters were ultimately carrying the risk of shipping.