Malcolm Turnbull and Julie Bishop have accused the opposition defence spokesman, Stephen Conroy, of “escalating tensions” over the South China Sea.

Bishop, the foreign affairs minister, criticised Conroy’s proposal to conduct freedom-of-navigation exercises within 12 nautical miles of Chinese structures in the South China Sea and said the opposition leader, Bill Shorten, had expressed unity with the government’s position.

Both Bishop and Shorten said operational details of freedom-of-navigation exercises were a matter for the military, and did not call for such operations within 12 nautical miles of Chinese rock outcrops or artificial islands.

On Wednesday Conroy told Radio National Australia should stop “pretending” to conduct freedom-of-navigation exercises and take more concrete action in the South China Sea.

On Tuesday an international tribunal in The Hague overwhelmingly favoured claims by the Philippines over China in the South China Sea.

Conroy said: “Now that it’s very clear you can’t build an artificial island and claim rights around it – there is no 12-mile limit around these islands ... Australia should authorise its forces to both sail and fly over those areas of the South China Sea.”

Australia supports in principle freedom-of-navigation exercises conducted by the US within 12 nautical miles of Chinese structures but has so far not conducted such exercises.

At a press conference on Wednesday, Bishop said: “Stephen Conroy is urging an escalation of tensions ... I think that’s a highly irresponsible call at this point.

“The Australian defence force will continue to exercise the international rights of freedom of navigation and freedom of overflight, as we have done in the past, but I wouldn’t go into the details of ADF operations. We don’t do that and we’re not about to start.”

The prime minister said Conroy was “steaming in a direction all of his own”.

“Everyone else in the region is calling for calm, consideration,” Turnbull said. “I think one our Asean neighbours called for sobriety in the way in which the decision was absorbed and considered, and only senator Conroy appears to be calling for an escalation of tensions.

“I’m relieved that [Bill] Shorten and the shadow foreign minister [Tanya Plibersek] are not taking the same approach.”

When asked at a press conference earlier on Wednesday whether Australia should conduct freedom of navigation exercises within 12 nautical miles, Shorten said only: “I believe that our naval forces and indeed our defence forces should be authorised to conduct freedom-of-navigation operations.

“Of course, the operational detail of that should be left to our military.”

Shorten said he wanted to present a “united front” with Turnbull. But freedom-of-navigation exercises should be authorised “in international waters and the ruling has made clear what international waters are”.

Shorten said he understood the point Conroy was making but Labor’s position was that “we don’t want to see unilateral actions, we don’t want to see escalation”.

“On matters such as the rule of law, international rule of law, the UN conventions and law of the sea, let this nation speak with one voice,” he said. “We don’t want to escalate and ratchet up tensions, but we don’t want to see unilateral actions either.”

Conroy said China had indicated it would ignore the ruling and its actions had become “even more aggressive and provocative, including sinking vessels and ramming vessels”.

Asked about the threat of economic repercussions if Australia conducted freedom-of-navigation exercises, Conroy said it was “straight-up bullying” to threaten retaliation.

“It is vital that we not just talk the talk but that we act and be seen to act to support the system,” he said. “The government is continuing to pretend to the Australian people that it has an ongoing program of freedom-of-navigation exercises. This is in fact not the case.”