Andy Burnham has said he would take his responsibilities to fund the defence investment plan “extremely seriously” if he becomes prime minister.
The plan, published on Tuesday, provided a £15bn spending boost to defence but is projected to leave the next prime minister with a £4.7bn funding gap to fill.
Burnham told LBC he had not seen all of the details prior to its publication but insisted there would be “no compromise on the security of the nation”.
The Makerfield MP also rejected attacks on his economic stance, insisting he would not be “indisciplined” on public finances.
He has faced criticism in the past for arguing, external that the UK had “got to get beyond this thing of being in hock to the bond markets”.
In his first media interview since announcing his bid to become PM, Burnham said the finances in Greater Manchester had been “rock solid” when he was mayor – and pointed to his previous experience working in the Treasury.
Labour’s 2024 election manifesto included a pledge not to increase taxes on “working people”, including National Insurance, income tax and VAT.
Asked if he would stand by those commitments, he said: “I stick by the manifesto and the promises that it made.
“So, let me be absolutely clear about that, but there is some room within that manifesto for movement on tax.”
He pointed to the possibility of increasing business rates on warehouses and major developments in order to cut the tax for pubs and some high street businesses.
On welfare, Burnham said he would not make “crude cuts to benefit levels that just put people who are struggling in even worse poverty”.
He said he would try to reduce the benefits bill by changing the education system to ensure better support for young people pursuing technical qualifications and providing work placements for 16 year olds.
He also said he wanted to see mental health support provided for those in work.
Burnham remains the only candidate in the race to replace Sir Keir Starmer and is expected to take over as prime minister on 20 July.
One of the biggest items in his in-tray will be the question of how to fund the UK’s rising defence spending.
On Wednesday, Conservative leader Kemi Badenoch accused Sir Keir of “leaving this mess to his successor” and asked if Burnham had agreed to fund the shortfall.
Asked by Andrew Marr on LBC whether he was aware of the funding gap before the defence investment plan was published, Burnham said: “I wasn’t in all of the discussions, but to be fair, the government had had an internal process ongoing.
“I regard it as something that the country has to face up to very seriously.
“We’re in a changing world. The nature of the threat is changing.
“What I can say to you tonight is I will take my responsibilities fully to fund the defence investment plan, if I am in the position to do so, I will take those responsibilities extremely seriously.”