He’s only two weeks into the job and Andy Burnham has already been hit with his first deadline.

A British commander warned the prime minister on Thursday that he needs to make his defence spending commitments clear by the autumn – or risk losing his support.

General Sir Richard Barrons, who co-authored the 2025 Strategic Defence Review, warned “a much more challenging discussion about what do you really think you’re doing with this government” awaits Burnham if he has not outlined plans by September or October.

His words follow a week where ministers repeatedly refused to commit to the previous target of spending 3% of gross domestic product (GDP) on defence by 2030.

It’s an obstacle which proved fatal to Keir Starmer’s premiership.

John Healey resigned as defence secretary over a lack of spending for his department in June, something which helped to accelerate the former prime minister’s downfall.

By making Healey his chancellor, Burnham has sent clear signals that he will respect demands to hike up the department’s budget.

So why did the new defence secretary, Wes Streeting, only commit to the Nato pledge 3.5% of GDP on defence by 2035 – a date which is in the next parliament – this week?

He told broadcasters that while the government is not “ruling out” the 3% spending commitment by 2030 but added: “It’s really important we set out how it will be paid for.”

While a very reasonable observation – a marker of how the Burnham cabinet is already building a reputation for more transparent communication – worries about defence investment are hardly new.

Russia’s invasion of Ukraine started more than four years ago and the Israel-Hamas conflict in Gaza has been raging since 2023.

Chair of the defence committee, Labour MP Tan Dhesi, told HuffPost UK that the government “must set out a clear plan for meeting its defence spending targets, with specific milestones and deadlines.”

He said the committee has already called for defence spending to reach 3% of GDP in this parliament.

Dhesi warned: “With the prospect of a Russian attack on a Nato ally before 2030, we cannot afford to delay. Investment in the UK’s defence and security must be accelerated as a matter of urgency.”

There’s also the matter of the “black hole” in the £15 billion defence investment plan (DIP) which Starmer failed to fully cost before he left office.

The Treasury only found £10.3 billion in departmental savings, meaning Burnham will have to find £4.7 billion in his autumn budget.

Even if the DIP were fully-funded, it would only take the UK to 2.7% of GDP from 2027-28.

It’s not just Burnham’s defence policies under scrutiny over potential cost, either.

His policy blitz from the last two weeks has seen him live up to his promise of putting the cost of living at the heart of his government.

The PM has promised to cut VAT from energy bills, a move expected to cost £850m.

The government said this would be funded via the cancelled digital ID programme.

However, former cabinet minister Darren Jones said the tax cut was “unfunded” because there had never been an extra pot of money for digital ID.

Burnham also announced a £500m plan to cap bus fares at £2 from January until the end of 2027 outside of London.

Most of the funding will come from money reserved for climate and energy projects, despite worries about the international impact.

The PM revealed a 20% cut in business rates for pubs and clubs too, which will cost £100m a year.

That will be funded by removing business rates relief from businesses which do not “make a positive contribution” to local communities, though the exact details remain unclear.

Burnham’s daily policy announcements have effectively boosted his support among voters and stopped him from looking like Starmer 2.0.

Labour has overtaken Reform in some polls for the first time in 16 months, with Survation putting Burnham’s party on 26% compared to Nigel Farage’s 24%.

Deltapoll and YouGov put the parties neck-and-neck, while More in Common found Burnham’s approval rating has soared to heights Starmer never reached.

But, as Savanta’s political research director Chris Hopkins warned, this could go into decline when the PM has “actual difficult decisions to make”.

He told HuffPost UK: “Burnham has started well, and his policy blitz, well-received by commentators, will begin to trickle down to the public.

“At this stage, though, the bounce is more likely to be less about Burnham the man and more about what he is trying to represent – a break from ‘politics as normal’.”

But he noted: “Where this has the potential to fall down is when he has actual difficult decisions to make.

“He’s already discussed using up his political capital to reform social care, something that has made PMs before him, namely Theresa May, come unstuck with the electorate.

“There is a danger that his popularity will fall, and fall quickly, as soon as he tries to address the challenges his predecessors failed to.

“It is in that sense that his honeymoon may only last so long, before the reality of governing effectively causes him the same problems it has previous prime ministers.”

More in Common’s Louis O’Geran offered a similar warning that his time in the sun might not last very long.

The external affairs manager told HuffPost UK: “There’s no doubt that changing leader mid-term has given Labour and the new PM breathing space.

“After a couple of weeks of popular announcements, Labour’s standing in our latest poll has risen to its highest since the early months of Keir Starmer’s government, and Burnham’s own approval rating now surpasses Starmer’s all-time high.

“However, it’s still very early days, and we’ve only seen a small number of polls so far. What these results tell us most of all is how volatile public opinion has become.”

Burnham will most likely be able to enjoy a few weeks of rising in the polls across the summer.

But, when MPs return from recess, parliamentary scrutiny resumes and pressure rises ahead of his first Labour conference as leader, real life will hit for voters as they realise the money has to come from somewhere.

Will Burnham be able to retain his newfound support once the cost of his promises start to come in?