Allies of Gavin Williamson, the UK defence secretary, have moved to quash reports that he had threatened to topple the prime minister unless defence spending was increased, but warned there was significant backbench anger over Theresa May’s refusal to confirm the UK would remain a “tier one” military nation.

Williamson is scheduled to meet Philip Hammond in the next fortnight in a attempt to secure concessions ahead of a Nato summit in Brussels in July, following a tense meeting with May and the chancellor last Tuesday, which ended without any promise of further funding.

After the meeting, May declined to confirm the UK should remain a “tier one” military power, a defence term referring to the full spectrum of military capabilities, including nuclear weapons.

May said only that the UK was “a leading defence nation”, despite being asked to use the specific phrase “tier one”.

Conservative MPs have expressed concern both privately and publicly about the comments. “There is certainly a large cohort of backbench Tory MPs who were deeply concerned at the lack of backing for the UK remaining a ‘tier one’ nation,” one defence source said.

“It would be massively reassuring for the party and the military if she was to confirm it and use those terms.”

Williamson’s lobbying for more funding was backed by Julian Lewis, the chair of the defence select committee, who said the MoD needed similar sums like the £20bn extra given to the NHS “just to stand still”.

He added: “There needs to be no political risk to the PM if she does the right thing. I’ve been in parliament 20 years and have never known such unanimity.”

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However, some Tory MPs have voiced frustration at the tactics of some cabinet ministers.

The former minister Nick Boles hit out at Williamson on Twitter, but also voiced frustration at the conduct of other cabinet ministers such as Boris Johnson, who after being asked at a reception about bosses’ concerns over Brexit, reportedly replied: “Fuck business”. He tweeted:

Nick Boles MP (@NickBoles) Would it be too much to ask that senior members of the Cabinet behave like grown-ups, discuss serious issues in a serious way, and avoid running to the papers with childish threats or swearing at foreign dignitaries?

In a coded warning to her cabinet colleagues, the chief secretary to the Treasury, Liz Truss, is set to warn in a speech that it is “not macho” to demand more money for their departments and they should concentrate on fiscal discipline.

“It is a tougher skill to demand better value for money and challenge the blob in your department,” she will tell the LSE on Tuesday, and add that the NHS funding boost was “exceptional”. Truss met Williamson this week to discuss defence spending, along with May and Hammond.

A source close to the row said Williamson was “genuinely passionate about the military getting the right resources” but said it was far-fetched to suggest he was threatening May.

“To suggest that the defence secretary is behind a plan to bring down the prime minister is absurd,” the source said. “He has been one of the most loyal people since she became prime minister, he never lost a vote as chief whip, he helped her broker the deal with the DUP to stay in power so she could keep her job and he continues to be her rock in cabinet.

“Any other suggestion is completely unfounded. But as a former chief whip, he’s only too aware of the strength of feeling on the backbenches and people have been very vocal in their warnings.”

The shadow defence secretary, Nia Griffith, told the BBC’s Andrew Marr Show Williamson was having “tantrums”, adding: “We don’t know for one minute whether he’s actually going to get that money.”



On Sunday, defence minister Guto Bebb defended the government’s strategy, saying it was “meeting the Nato target and increasing the defence budget in real terms ever year”, but added it was “laughable” that Labour would spend more on defence.