Labor’s Senate leader, Penny Wong, has warned Bill Shorten not to damage the party’s hard-won unity as she throws her support behind leftwinger Anthony Albanese to lead the opposition to the next election.

As the party embarks on an internal leadership contest that will see MPs and party members choose between Albanese and the shadow treasurer, Chris Bowen, Wong issued a thinly veiled warning to Shorten to stay out of the process.

“I would be surprised if that were occurring,” Wong said about reports that Shorten was actively trying to block Albanese from the leadership. “I’d be surprised because it’s not consistent with the role he now has, and I’d be surprised because it would potentially undermine the very unity he has been part of developing and building in opposition.”

Shorten is rallying caucus MPs to vote against Albanese because of the long-running animosity between the two, but the intervention is seen as bolstering Albanese’s standing internally given the disastrous election result.

Bowen has said he does not expect the caucus vote will bind MPs along factional lines, with several high-profile members of the right, including Kristina Keneally and Tony Burke, indicating they will support Albanese.

Queenslander Jim Chalmers, another rightwinger, is yet to declare whether he will also contest the leadership.

Keneally, who was Shorten’s “bus captain” and a high-profile member of the campaign, said that while she was a friend of Bowen, she recognised the need to change direction.

She wrote on Twitter: “In light the election outcome, we need to reframe our policies and we need to listen to our members & supporters. We must reconnect with working people who did not vote for us. It’s my view that Anthony Albanese @AlboMP is best placed to do that.”

Bowen has defended the party’s unpopular economic policies, of which he was a key architect, pledging to start with a review of the party’s platform and a “blank canvas” if he becomes party leader.

The shadow treasurer conceded the party had “paid a price” for its tax reform agenda but has disputed it was the main reason for Saturday’s disastrous result.

“There’s a whole lot of factors … for our defeat, which was a kick in the guts for us and everybody who was relying on a Labor government,” Bowen said. “I’m deeply respectful of the verdict the of Australian people on Saturday, which means we have to start again with a fresh canvas, and think about how we implement those values.”

As Bowen said he believed he had majority support in the right-faction-dominated caucus, other leftwingers on Wednesday also publicly declared support for Albanese including, Murray Watt, Terri Butler, Graham Perrett and Andrew Giles.

“He is the person to bring our movement together, to articulate our enduring values as a compelling case for change, to stand up to Scott Morrison’s regressive agenda and to secure the government that all Australians need,” Giles said.

Describing Albanese as the “outstanding parliamentarian of our generation”, Wong said her factional ally was “a man of authenticity and integrity.”

“He’s got a capacity to speak to people across this great country, to speak to people in the regions and in the outer suburbs, as well as in our cities.”