Opposition MPs have reacted furiously after Downing Street confirmed that work to paint a military plane used by the Prime Minister in the colours of the Union flag will cost almost £1 million.

The grey RAF Voyager jet is currently receiving a pre-planned makeover at an airport in Cambridge, with one defence source reportedly saying the new design sounded like something “from Austin Powers”.

Confirming the red, white and blue paint job, Downing Street said the work would cost “around £900,000” and would mean that the plane can better represent the UK around the world with “national branding”.

But criticising the size of the bill, acting Lib Dem leader Sir Ed Davey compared it with the cost of drugs used to treat Covid-19 patients.

Sir Ed tweeted: “The drug dexamethasone, that can potentially save the lives of people with coronavirus, costs £5 per patient.

“Boris Johnson could have bought 180,000 doses of that, but instead he’s painting a flag on a plane.”

Labour shadow minister Emma Hardy said: “For goodness sake. Please can we have a grown up as a Prime Minister instead of a child.”

And her fellow Opposition front bench colleague Justin Madders tweeted: “What’s he painting it with, gold leaf?”

The SNP lambasted it as an “utterly unacceptable use of public funds”.

Stewart McDonald MP, the party’s defence spokesman, said: “Boris Johnson is taking yet another page out of the Trumpian playbook with this cynical move – distracting from the reality of his Government and chief adviser’s conduct over the past few months.”

There was even a call from the Government benches for the Ministry of Defence (MoD) to be spared being lumbered with footing the bill.

Tobias Ellwood, chairman of the Commons defence committee, tweeted: “Yes to patriotism!

“But at the tune of £900,000 – Cabinet not MoD should pay.”

But the Prime Minister’s official spokesman pointed out that the PM was not the only who uses the jet.

He said: “The RAF Voyager used by the royal family and the Prime Minister is currently in Cambridgeshire for pre-planned repainting.

“This will mean that the plane can better represent the UK around the world with national branding, similar to many other leaders’ planes, while also retaining its military air-to-air refuelling capability.”

The spokesman defended the £900,000 cost, telling reporters: “That incorporates the cost of creating a design that will promote the UK around the world without compromising the plane’s vital military role.

At every stage we have worked to ensure value for money for the UK taxpayer and all of the work has been undertaken in the UK, directly benefiting British suppliers

“At every stage we have worked to ensure value for money for the UK taxpayer and all of the work has been undertaken in the UK, directly benefiting British suppliers.”

Culture Secretary Oliver Dowden, asked about the repainting costs at the daily Downing Street briefing, backed the outlay on splashing the plane with fresh branding.

“I think that we have always spent money on promoting the UK around the world,” he said.

“I see this with creative industries – we genuinely are a creative industries superpower and we should be promoting that and we’ve done that through the great campaign.

“I think that the work on Voyager is part of that promotion.”

Sky News previously reported a defence source saying the paint job sounded like something “from Austin Powers”.

Mr Johnson has previously questioned why the plane is grey, saying he would like to have a “Brexit plane” to help him travel the world and promote the Government’s vision of global Britain.

He also complained in 2018 while foreign secretary that the RAF Voyager jet, which is shared by the Prime Minister, senior Cabinet members and the royal family, “never seems to be available”.