As Rachel Reeves hosted a charity breakfast in the grand state room at No 11 Downing Street last week, she stood beneath an 18th-century portrait of a politically powerful woman from another era: Sarah Churchill, Duchess of Marlborough.

Part of Reeves’s feminist rehang, the painting of Queen Anne’s confident right-hand woman, resplendent in velvet, underlined how visibly different the Treasury now looks under the leadership of the first female chancellor.

Yet seven tumultuous and bruising months into her tenure, critics complain that far from being given a radical makeover, the Treasury has reverted to type as the department that likes to say “no”.

“I always wondered why anyone who had left government always railed against the Treasury. Now the scales have been lifted from my eyes,” said one Labour adviser.

One senior thinktanker with close links to government said: “There’s a real sense from outside the Treasury of institutional capture.”

Reeves’s allies firmly reject that characterisation and hint that it includes an undertow of sexism.

The chancellor gave her own justification for making tough decisions on the public finances on Sunday, telling the BBC: “It wasn’t the wealthiest who lost out when Liz Truss lost control of the economy, it was ordinary working people.”

Reeves’s maiden budget in October was a bumper tax and spending package, including plans to set aside an additional £100bn for public investment, for which Treasury officials complain the press do not give her sufficient credit.

With a 10-year infrastructure strategy in the works, Wednesday’s spring statement is likely to highlight where some of this capital spending will go.

Reeves has also dialled up the Treasury’s focus on growth to try to counter longstanding concerns that it is primarily a finance ministry, too motivated by squeezing spending. She has begun weekly progress meetings with officials on growth, alongside those on tax and spending that have long been in chancellors’ diaries.

After the increase in employer national insurance contributions in the budget led to a business backlash, and as official GDP data disappointed, Treasury messaging switched relentlessly to “kickstarting growth”, with the chancellor promising repeatedly to move “further and faster”.

She hammered home this message by announcing at the World Economic Forum in Davos in January that, despite having once promised to be the “first green chancellor”, she now saw growth as a higher priority than net zero.

She went on to underscore that by backing a third runway at Heathrow in a speech later that month. Some Treasury officials were sceptical about the need for such a speech, but Reeves saw it as a forcing mechanism for pushing through policies.

While the chancellor’s team were delighted with this new year reset, the past few weeks at Westminster have been dominated by her decision to press for £5bn of welfare cuts before this week’s spring statement.

The looser definition of debt Reeves adopted allowed her to increase borrowing significantly without busting her new fiscal rules, making space for that infrastructure splurge.

But she has set a strict target for matching day-to-day spending with tax revenues and this is the rule that is threatening to bite, prompting Reeves to look for cuts.

In Labour’s early weeks in power last summer, progressive economists did battle on WhatsApp with colleagues who had gone into government, telling them that there was no economic necessity for immediate spending cuts.

Reeves and her team had been given a hair-raising briefing by officials who warned them that bond markets rattled by Truss’s tax-cutting spree would punish the new chancellor unless she showed a willingness to take tough decisions.

One person involved in one of these WhatsApp debates recalls that the insiders said they had received secret briefings, the contents of which they couldn’t divulge.

Reeves took the decision to show that she was serious by slashing the winter fuel allowance, though she also granted above-inflation pay increases to many thousands of public sector workers to draw a line under months of disruptive strikes.

Policy wonks who have watched Reeves along the way to No 11 say her economic views have shifted over the years.

In a 2018 pamphlet called the Everyday Economy, written after Labour’s better than expected showing in the general election a year earlier under Jeremy Corbyn, Reeves called for “a radical overhaul of the tax system because our current system of wealth taxation is not working” and suggested that “old and new monopolies need to be broken up to ensure that markets are competitive”.

In government, she has eschewed wealth taxes – aside from on farmers’ estates – and overseen the chair of the competition regulator being forced out in part because businesses had complained.

Reeves-watchers are divided about whether her embrace of strict fiscal discipline is an unfortunate result of the extremely unlucky hand she has been dealt or a deep-seated belief.

One Labour-supporting economist said her views had evolved towards “something almost undetectably different from Treasury orthodoxy”, adding: “I think in the end it reveals what was previously unknown – which is that she is a fiscal hawk.”

However, those with knowledge of her team’s thinking say Reeves has become increasingly willing to challenge civil servants since the winter fuel decision which was widely seen as a political misstep.

As the first Labour chancellor to encounter the back and forth of the Office for Budget Responsibility’s (OBR) forecasting round first-hand, allies say Reeves’s team has also become more sceptical about whether the process – established by George Osborne – is optimal.

One drily described the OBR’s unyielding director, Richard Hughes, as the “third man” in economic policymaking, adding that the forecasting round had been a “fascinating rollercoaster”.

As a boss, Reeves commands intense loyalty: her staff say she is hardworking, committed and energetic, but can be stern when disappointed by the quality of an official’s work.

One minister points to the fact that the chancellor has trackers that monitor the progress of a slew of policies she has announced, including on issues outside the Treasury’s core brief, such as planning or infrastructure.

Like Gordon Brown, Reeves has tended to be the driving force of domestic policy, with Keir Starmer, without a strongly held economic stance of his own, trusting her to lead. However, Labour insiders say there has been much closer cooperation with No 10 in recent months.

With Whitehall departments being asked to set out the impact of potential cuts before June’s spending review, it is increasingly Reeves, not Starmer, who is the lightning rod for discontent.

A Survation poll of Labour members put Reeves at the bottom of a league table of cabinet members, with a -11% approval rating. Ed Miliband, at the top, scored +69%.

Labour backbenchers who have known Reeves as she has progressed up through the party say she is a good colleague, steeped in the party since joining as a teenager.

She puts in more frequent appearances in the House of Commons tearoom, where MPs go to let off steam, than Starmer, and hosts groups of backbenchers for drinks and chitchat. Cross-departmental issues are as often resolved over breakfast with a fellow cabinet minister.

And like Theresa May when she was prime minister, Reeves is not too grand to muck in with local party functions. She appeared at the Yorkshire Labour Conference this month, fresh off the plane from a G20 finance ministers’ meeting in Brazil.

One close ally rejects the characterisation of Reeves as captured by the Treasury, insisting that instead she has risen to the moment by giving the institution a clear sense of direction. “The point is, in the current environment, you want someone who can make a decision, and gets the question that’s being asked, and that’s definitely what she’s got.”