Rebecca Long-Bailey has made her opening pitch for the Labour leadership, avoiding any direct criticism of Jeremy Corbyn but implicitly offering an alternative approach by promising to champion “progressive patriotism”.

In her first substantive comments on the election result, the party’s worst in terms of seats won since 1935, the shadow business secretary uses an article for the Guardian to say Labour’s “compromise solution” on Brexit was partly to blame, but that trust was also an issue.

Without formally announcing her candidature, she confirms she is considering standing – and that she would back Angela Rayner, the shadow education secretary, for deputy leader, effectively creating an all-female, all-working-class joint ticket.

When Corbyn announced the day after the election that he would resign, Long Bailey was immediately installed as favourite by some bookmakers. Labour plans to open the contest early in the new year and have a new leader installed by the end of March.

Two candidates, Emily Thornberry and Clive Lewis, have already formally declared they are standing and at least five more MPs have used interviews in the last fortnight to say they may join the race. Long Bailey, who has been nurtured by Corbyn’s team for a while as their preferred successor, has kept away from the media and avoided the debate that has engulfed Labour about what went wrong.

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Breaking her silence in the Guardian, she says the party needs to have an honest discussion about why it lost and that “it’s no good having the right solutions if people don’t believe you can deliver them”.

Apart from saying that Labour’s compromise policy on Brexit “satisfied too few”, she does not explicitly criticise the way the party managed the election campaign or Corbyn’s qualities as a leader, despite numerous polls and much anecdotal evidence to suggest his unpopularity was a major hindrance.

She also says Labour’s policy agenda was popular: “We didn’t lose because of our commitment to scrap universal credit, invest in public services or abolish tuition fees.”

Her article does not mention the party’s handling of antisemitism, but Sir Keir Starmer, the shadow Brexit secretary and probably Long Bailey’s most formidable rival for the leadership, cited the issue in one of his early assessments of the reasons for the election defeat.

Long Bailey differentiates herself from Corbyn by saying that as Labour leader she would champion “progressive patriotism”. She says: “From ex-miners in Blyth Valley to migrant cleaners in Brixton, from small businesses in Stoke-on-Trent to the self-employed in Salford, we have to unite our communities. Britain has a long history of patriotism rooted in working life, built upon unity and pride in the common interests and shared life of everyone.

“To win we must revive this progressive patriotism and solidarity in a form fit for modern Britain.”

Corbyn rejected the charge that he was unpatriotic, but Tory claims to the contrary based on his frequent opposition to British military endeavours and his failure to sing the national anthem at a church service in the early days of his leadership, did enormous damage to his public standing.

Long Bailey also implies in her article that Corbyn has not gone far enough in giving Labour members control over the party. “Our promise to democratise society will ring hollow if we can’t even democratise our own party,” she says. An olive branch to the Labour left, this echoes one of the main arguments Clive Lewis has made in his pitch for the leadership.

Long Bailey also writes about her childhood in Salford, saying that her family had to move when the docks where her father worked closed, but that the threat of redundancy continued in his new workplace. This line seems to have been included to address a critical report in last week’s Sunday Times claiming that one account she gave of remembering job losses at the Salford docks as a child was misleading because she was only very young when the docks closed.

As well as Long Bailey and Starmer, who are all but certain to declare, and Thornberry and Lewis who have declared already, Lisa Nandy, Jess Phillips and Yvette Cooper are seriously considering joining the contest. David Lammy and Ian Lavery are possible candidates too, and Dan Jarvis has refused to rule himself out.