A former Labor frontbencher, Kim Carr, has challenged his party’s repositioning post-election, asking why the ALP would decline to vote against government legislation that contravened the party’s national policy platform.

Carr’s pointed intervention came during a caucus meeting where the Labor leader, Anthony Albanese, told colleagues the Coalition would get most of its legislation through the Senate in this parliament because there was an effective conservative majority post-election.

It also came as the former Labor leader, Bill Shorten, in his first television interview since losing the May election, said: “Labor will still be a very determined opposition and we will still keep advocating our values.”

Tuesday’s discussion was triggered by legislation giving effect to some of the recommendations from the royal commission established by former Labor prime minister Julia Gillard. The government legislation concerns combating child sexual exploitation and, according to Tuesday’s briefing, contains mandatory minimum sentences for some offences.

The recommendation from the relevant shadow minister, Kristina Keneally, was that Labor not oppose the bill in the House of Representatives, and the shadow cabinet make a final decision about how to proceed after a Senate inquiry. She indicated the legislation would come back to caucus.

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People present at Tuesday’s meeting said Keneally gave the impression that Labor could ultimately support the bill, prompting Carr to challenge the New South Wales frontbencher, asking why Labor would vote for legislation that contravened its platform.

The 2018 platform agreed to at the party’s national conference last December says Labor opposes mandatory sentencing and detention regimes.

A number of frontbenchers supported Keneally, including Joel Fitzgibbon who, according to one account, suggested Labor did not need to be guided by the platform on this issue. The shadow attorney general, Mark Dreyfus, supported Keneally’s recommendation but outlined why Labor was opposed to mandatory sentencing.

The caucus debate came as Albanese used Tuesday’s meeting to tell colleagues the opposition has washed up post-election in a parliamentary position not unlike the position Labor faced in 2004, when Mark Latham lost the election against John Howard, and the Coalition gained control of the Senate.

He predicted there would be a number of situations in the 46th parliament – like the recent debate around the Morrison government’s tax cuts – where Labor pursued amendments but did not vote against the proposal at the third reading because the proposal under consideration contained elements that the opposition supported.

In relation to Tuesday’s proposal on legislation giving effect to Gillard’s royal commission, arguments were made that Labor needed to ensure the key recommendations of that inquiry were delivered, even if that created a conflict with the platform.

Outside the caucus debate, Shorten told the ABC that Labor’s loss in May was “very disappointing for the nation, for the people who voted for Labor, and very disappointing personally”.

“To the millions of Australians who voted Labor, Labor will still be a very determined opposition and we will still keep advocating our values.”

He said the looming campaign review would identify the problems in the campaign “and we will have to learn our lessons”.

Shorten described the defeat as “very disappointing, and disappointing for me, and I think disappointing for a lot of people, but nonetheless it has happened, that’s democracy. As I said on the night, the people have expressed their view so we need to move on and be the best possible opposition.”