Brussels’ former top law officer has rubbished Boris Johnson’s extraordinary plan to sabotage the EU and make it ‘no longer legal’, arguing it makes no sense.

Downing Street has threatened to render the bloc no longer “legally constituted”, paralysing its decision making, to force EU leaders to cave in to the UK’s demands.

But Jean-Claude Piris, formerly the director-general of the EU Council’s legal service, said the idea – refusing to appoint a new commissioner – would fail to shut down the EU, as No 10 hoped.

“The Commission can continue to work and decide legally,” Mr Piris wrote on Twitter, citing a precedent dating back to 1999.

Instead, he said: “The UK will be brought to the EUCJ [the European Court of Justice] for violation of its obligation.”

Richard Corbett, the leader of Labour’s bloc of Euro-MPs, echoed the criticism, tweeting: “Nonsense idea that Johnson could paralyse EU to force it to expel UK.

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“If he refuses to nominate a Commissioner, the UK would be in breach of the treaty – that being so, EU Commission not at fault and can operate legally.”

In a dramatic escalation of its battle with Brussels, No 10 believes it can put the EU in breach of its own legal duty for all 28 member states to be represented on its executive branch.

The UK would be “disrupting” Brussels life to such a degree that member states will then make it clear they will refuse to grant an Article 50 extension – even if asked for – it hopes.

A source told The Independent: “We will turn the pressure onto the EU to show how difficult it will be for them if the UK is still hanging around.”

The aim is to force an acceptable Brexit deal, but the source added: “If they won’t negotiate a deal, it would be ideal if they would kick us out.”

The threat to bring the EU to a standstill is a hugely-controversial attempt to break free of the ambush which saw MPs move to block a no-deal – while also denying Mr Johnson the general election he craves.

Dominic Raab, the foreign secretary, has now revealed the government will go to court to challenge the order from parliament to delay Brexit.

He insisted the government would not break the law – after MPs passed legislation requiring Mr Johnson to seek an Article 50 extension – but said it would not comply either.

Vowing to “test to the limit” what the new law demands, Mr Raab said: “We will look very carefully, legally at what it requires and what it doesn’t require.”

And, pointing to the failed legal actions to stop parliament being suspended, he told Sky’s Sophy Ridge programme: “We had two legal challenges last week and we won both of those.”