Where the Conservatives had “there is no money”, Labour now has “the things we shamefully left undone”.

The government has spent much of its first week in power pinning the blame for its politically sensitive decisions on the previous incumbents, much as the Conservatives did after 2010.

The Tories were helped in that strategy by a note left by the departing Treasury chief secretary, Liam Byrne, admitting to his successor: “I’m afraid there is no money.”

On Friday Labour sources believed they had been given a similar political gift when the former home secretary Suella Braverman tweeted: “We’ve all got to start taking responsibility for what we did. And for the things we shamefully left undone. Like not building enough prisons.”

Senior Labour officials say they intend to spend much of the following few years attacking the Conservatives with the same vigour as they did during the election campaign.

The strategy is based on that of David Cameron and George Osborne after the 2010 election, when their repeated message that Labour had crashed the economy not only gave political space for spending cuts but also helped deliver a majority in 2015.

One Labour strategist said: “We were incredibly disciplined in the run-up to the election in the argument we were making that we were inheriting the worst set of circumstances since the second world war, and we have got to be equally disciplined now we are in government. To govern is to campaign.”

Rachel Reeves, the chancellor, began that strategy on Monday, using her first set-piece speech as chancellor to argue: “We face the legacy of 14 years of chaos and economic irresponsibility.”

She presented new analysis showing that if the economy had grown at the same pace as those of other OECD countries, it would be more than £140bn larger by now. The chancellor intends to present an updated economic outlook from Treasury officials to parliament at some point in the next two weeks in a further effort to underscore her message.

Braverman’s tweet will be particularly welcome for Shabana Mahmood, the justice secretary, who sought on Friday to blame the Tories for her decision to release low-risk offenders from prison earlier.

Echoing the language used about supporters of appeasement in the 1930s, Mahmood said: “Those responsible – Sunak and his gang in No 10 – should go down in history as the guilty men. The guilty men who put their political careers ahead of the safety and security of our country. It was the most disgraceful dereliction of duty I have ever known.”

Labour will also be helped if the Conservatives decide to hold a leadership election that lasts several months, as Labour did in 2010 – a decision that many in the party now blame for it not properly countering the emerging Tory narrative.

“The fact that Labour did not have a permanent leader until autumn 2010, and that Ed Balls did not become shadow chancellor until 2011, definitely helped us cement our message,” said one former Conservative adviser.

Another Tory source who worked in the coalition government said: “We were able to use so many things to hammer home the point. It wasn’t just the Byrne note, it was also the warning from [the Bank of England governor] Mervyn King that we needed significant fiscal consolidation, and the comments from [the bond investor] Bill Gross that UK gilts rested on a bed of nitroglycerine”.

However, experts say the Tories are unlikely to recover their reputation for competence within the next few years, even without garish warnings from respected people in the financial services sector or ill-advised notes from departing ministers.

When the Tories lost their poll lead on economic competence in the 1990s, it did not return until 2008. Labour then did not regain it until Liz Truss’s ill-fated mini-budget of 2022.

Jane Green, a professor of political science at Oxford University, said: “Reputation on the economy tends to last for a very long time. Once a party has lost it because of an economic competence shock, they do not typically regain it until the other party suffers their own economic competence shock.

“In other words, the Tories will recover their reputation on the economy if and only if the Labour government is seen to have done something massively wrong.”