Another blow for international dairy prices.

Fonterra's latest Global Dairy Trade Event has seen a 4.9 percent drop in prices overnight.

It follows a minor reprieve a fortnight ago, however prices have been dropping steadily in 2014 - falling by more than 25 percent since February.

Whole milk powder was down 5.4 percent, with six out of seven product categories dropping in value.

The price for butter dropped by over 13 percent.