However, Mr Morrison has defended his attention on Solomon Islands and insists Australia is still the South Pacific nation's first port of call.

After it was announced by the Chinese Foreign Ministry late on Tuesday, Solomon Islands Prime Minister Manasseh Sogavare confirmed to the nation's parliament on Wednesday that the deal was signed a few days ago.

He said the deal was needed to cover "critical security gaps" and his country is not seeking to "undermine the peace and harmony of our region". It had been flagged for weeks and had caused a chill in defence circles with expectations it will lead to the establishment of a Chinese military base in the South Pacific.

In recent days - and in the middle of the election campaign - Senator Seselja was dispatched on a mission to the capital Honiara in a last-minute attempt to stop the deal, but it is now clear the mission failed.

"[This is] one of the greatest policy failures that we've seen from this government," Mr Albanese said.

"This deal between China and the Solomons was foreshadowed, foreshadowed last August, the government was warned. Yet, only in recent days did the government bother to send a junior person across to the Solomons."

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Senator Seselja was also described as a "junior woodchuck" by Labor's foreign affairs spokeswoman Penny Wong, who also referred to the pact as Australia's worst foreign policy failure in the Pacific since the end of World War II. The warning in August was given by Solomon Islands' Opposition Leader Matthew Wale.

Top United States official, National Security Council Indo-Pacific Coordinator, Kurt Campbell is due to visit Solomon Islands later this week.

The Morrison government is "deeply disappointed" by the signing of security pact and is concerned about transparency, with Mr Morrison saying it highlights the "incredible pressure on Pacific nations that comes from China seeking to undermine the security of the region".

"We still have the priority relationship there. We are still the first call," he told Adelaide radio 5AA.

"We have Australian Federal Police there right now supporting them with what they're doing."

"We were the government that ensured we invested in the undersea cable there. We invested in their transmission project for electricity. We are their biggest supporter when it comes to overseas development assistance. And that is true all around the Pacific."

The Labor leader said if he was Prime Minister he would have sent Senator Wong instead of the Senator Seselja equivalent, which is currently Pat Conroy.

With his personal intervention in Honiara not working, Senator Seselja said he was "disappointed" and "concerned".

"There will be ongoing discussions," he told ABC radio.

"I've been engaging with leaders and counterparts in the region, both online .. but also in person in Brisbane."

"Last week, we had a number of senior leaders from the Pacific. I've spoken to New Zealand counterparts, counterparts from Fiji, from PNG, from Tonga and other nations in the region, the head of the Pacific Islands Forum.

Asked whether Foreign Minister Marise Payne should have been sent to Solomon Islands, instead of attending a fundraiser in Sydney, Mr Morrison said it was right for Senator Seselja to visit the nation and that Australia had calibrated its diplomatic response to the issue.

Senator Seselja said he had expressed to Mr Sogavare there should be transparency in the Solomon Islands' deal with China.

"We have raised our concerns and will continue to raise our concerns about what this means for our region," he said.

Former Coalition government foreign minister Julie Bishop weighed in on Solomon Islands' security deal with China, saying the South Pacific nation appeared now to have turned its attention elsewhere.

"While we don't have all the details, this could well mean there would be Chinese military bases on Solomon Islands and that really changes the dynamic and environment in our area, in our region," Ms Bishop said.

"I would be greatly concerned and I believe that our foreign minister should be on the next plane to Solomon Islands to talk with the government to see what's actually being agreed and how that impacts on the security in the region more broadly and also on Australia's security interests."

A draft security agreement between China and Solomon Islands was revealed this month to have been "initialled" by the two nations.

The pact raises the prospect China will establish a military base on the islands, which are only 1700 kilometres from Cairns.