New Zealand is paying its dues to Washington by giving the top secret Waihopai spy station in Marlborough sweeping new powers and technology to tap into the international phone calls which foreigners make across the Pacific.

Waihopai's satellite intelligence-gathering capacity is to be doubled in a move understood to be a pay-off to the United States for the continuing warming of relations in the wake of the breakthrough visit to Washington in March 1995 by the Prime Minister, Jim Bolger.

A special exemption to the Crimes Act will allow Waihopai to intercept the "private oral communications" of a foreign state, foreign organisation or foreign person which might yield foreign intelligence.

Some political sources last night suggested both the exemption and expansion, which will boost Waihopai's contribution to intelligence-sharing arrangements with United States, Australian and British agencies, was targeted at China following the closure of a British monitoring station in Hong Kong.

However, a researcher into intelligence matters, Nicky Hager, said the Hong Kong station had closed some time ago. He understood the boosting of Waihopai had been planned for several years by the Government Communications Security Bureau (GCSB), which runs the monitoring station.

Mr Hager said the exemption to the Crimes Act was a "startling" development because until now Waihopai had legally been able to intercept only non-voice communications such as faxes, e-mail and telex messages.

The law change effectively meant any call between a New Zealander and a foreigner could be intercepted.

News of the law change and the Waihopai expansion came in a statement yesterday from Mr Bolger, which announced the construction of a second antenna to be housed in another distinctive golfball-like "radome" at the site in the Marlborough countryside.

Mr Bolger said the new powers would be strictly confined to foreign communications that contained or might "reasonably be expected to contain" foreign intelligence. The GCSB was still forbidden from "intentionally" intercepting New Zealanders' voice communications.

Mr Bolger refused to supply a detailed explanation for the new powers, except to say the need for intelligence that supported the Government's foreign defence and trade policies had, if anything, increased in recent years.

He said increasing numbers of satellites had meant the "steady erosion" of the effectiveness of the sole antenna at Waihopai, which was built 10 years ago.

But Mr Hager said the new antenna would enable New Zealand to monitor the two Intelsat satellites that carry the bulk of communications across the Pacific.

Under previous intelligence-sharing arrangements, New Zealand had been responsible for monitoring one of those satellites. Waihopai would now monitor both satellites, freeing up an Australian sister station for other tasks.

Opposition parties have been briefed privately on the Waihopai expansion, but the Alliance [Party] was the only one to criticise the doubling of the size of a spy base designed to serve "foreign spymasters."