New Zealand has formally complained to the World Trade Organisation against Australia's quarantine rules governing the entry of apples from across the ditch, which have been imposed to prevent the spread of fire blight.

New Zealand has alleged there has been political interference in the quarantine process.

In 2007 Biosecurity Australia ruled that New Zealand apples could enter Australia, but only if a strict - and what the Kiwis claim is trade prohibitive - quarantine process is followed.

But Australian Trade Minister, Simon Crean, says the Government has lodged a "comprehensive rebuttal" in its submission to the WTO.

"Australia will defend its quarantine measures vigorously before the WTO dispute settlement panel," Mr Crean said.

"They are science-based and consistent with Australia's WTO obligations."

A WTO dispute panel will conduct hearings on this matter in early September.

* Australia's submission is available at www.dfat.gov.au.