Muscle-flexing Rishi Sunak 'is acting like he's already Prime Minister' as poll reveals his huge popularity compared to lagging Boris Johnson

'We are working on the basis that we need to be ready for power within a year.'

The words – spoken by a close ally of Rishi Sunak earlier this month – are likely to add to the unease in No 10 over the growing muscle-flexing by the Treasury as Boris Johnson battles the gravest public policy challenge for a British government since the Second World War.

Mr Johnson's aides are adamant that the traditionally fraught relationship between No 10 and the Treasury has been replaced by a 'new era' of harmonious co-operation.

But the party whips – who enforce discipline and provide Downing Street with intelligence on MPs' activities – are monitoring the increasing assertiveness of the Chancellor's operation. 

'We are working on the basis that we need to be ready for power within a year.' The words – spoken by a close ally of Rishi Sunak earlier this month – are likely to add to the unease in No 10 over the growing muscle-flexing by the Treasury as Boris Johnson battles the gravest public policy challenge for a British government since the Second World War

Mr Johnson's aides are adamant that the traditionally fraught relationship between No 10 and the Treasury has been replaced by a 'new era' of harmonious co-operation. But the party whips – who enforce discipline and provide Downing Street with intelligence on MPs' activities – are monitoring the increasing assertiveness of the Chancellor's operation

Ambitious backbenchers claim to have been approached by members of Mr Sunak's entourage about jobs in any future administration.

Allies of the Chancellor also claim Cabinet Office Minister Michael Gove, having accepted he is unlikely to beat Mr Sunak in a leadership battle, has been 'tacking close' to Mr Sunak in the hope he will succeed him in the Treasury. 

However, the allies say, Mr Gove is being kept at arm's length because 'Rishi doesn't trust him'.

Such chatter seemed inconceivable when Mr Sunak became Chancellor in February, after Sajid Javid was effectively ousted by adviser Dominic Cummings as part of an attempt to assert No 10's authority over the Treasury.

While Mr Javid had been dubbed 'Chino' – Chancellor in name only – Mr Sunak, who was then 39 and only five years into his political career, was called 'Baby Chino'. 

But after eight months of the Covid crisis, Mr Sunak's sure-footed public displays and multi-billion-pound bailouts have seen his poll ratings soar, while the Prime Minister's have sagged amid speculation about his physical and financial health and backbench rebellions.

In a Deltapoll survey for today's Mail on Sunday, Mr Sunak receives an approval rating of plus 31 points, while Mr Johnson receives minus 14 points. Now the Chancellor's subtle but steely displays in meetings risks turning Mr Johnson into 'Pino': Premier in name only.

After eight months of the Covid crisis, Mr Sunak's sure-footed public displays and multi-billion-pound bailouts have seen his poll ratings soar, while the Prime Minister's have sagged amid speculation about his physical and financial health and backbench rebellions

It has inevitably led to jealousy, with one Minister grumbling privately last week that Mr Sunak should 'stop behaving as if he is PM already'.

The Chancellor's hawkish stance on the lockdown chimes with the views of those Tory backbenchers who are determined to stop the economy from being completely wrecked by the restrictions – all serving to make Mr Johnson's 80-seat majority look much less comfortable than it should be.

Mr Sunak's growing power was demonstrated when he fought off attempts by Government scientists Chris Whitty and Sir Patrick Vallance to bounce Mr Johnson into a new 'circuit-breaking' two-week national lockdown, a performance so 'forthright and forensic', according to sources, that rumours spread that he had threatened to resign.

The claims were denied by the Treasury, but as infection levels continue to climb during the long-feared second wave, Mr Sunak is facing pressure for a 'Covid reset' with a pre-Christmas shutdown. 

Mr Sunak's political Teflon – he is effectively unsackable, as losing two Chancellors in such short order would be unthinkable for Mr Johnson – has led to a shift in some of the traditional alliances.

Allies of the Chancellor also claim Cabinet Office Minister Michael Gove, having accepted he is unlikely to beat Mr Sunak in a leadership battle, has been 'tacking close' to Mr Sunak in the hope he will succeed him in the Treasury. However, the allies say, Mr Gove is being kept at arm's length because 'Rishi doesn't trust him'

During a meeting last week to discuss the Treasury's plans to axe a multi-year Government spending review, the sources say Mr Johnson and Defence Secretary Ben Wallace joined forces with Mr Cummings – not previously one of Mr Wallace's biggest fans – in a 'doomed attempt to resist the Chancellor'.

Mr Sunak later announced that a one-year review would be held at the end of November instead to prioritise the Government's response to Covid and focus on supporting jobs until 2022.

A frustrated Mr Wallace, who is facing a £13 billion hole in his budget, spoke out the following day by warning that 'our adversaries will not halt in the absence of our strategies and the UK's defence can never be paused, in the face of financial uncertainty'.

A No 10 source insists Mr Johnson and Mr Sunak remain in lockstep as the Prime Minister 'threads a path through the Scylla and Charybdis of Covid' – a Johnsonian-style Greek mythology reference to the difficulty of choosing between economic and public health.

A Government source said: 'It is understandable that some Cabinet Ministers are sore about the decision to have a one-year review, which is where a lot of this rubbish about Rishi is coming from.

'There will be selected exemptions to allow some multi-year settlements, but it is not practical in the current conditions.

'It is nonsense to suggest that Rishi is planning any sort of takeover. Given everything that is going on, he wouldn't have the time, apart from anything else.'