Michel Barnier succeeded in briefly uniting British politicians on Wednesday with new demands for a Brexit transition agreement that instead raised old fears of a no-deal departure.

The proposal for special rules to punish the UK for flouting EU law during the 21-month period was predictably deemed “unacceptable” by hardliners such as Jacob Rees-Mogg, who already regard the notion of regulation without representation as akin to “vassal state” status. Nigel Farage compared the arrangement to Vichy France.

But even Liberal Democrats who want to stay in the EU voiced their disapproval at Barnier’s proposal. “This is the reality of Brexit – outside looking in and obeying their rules,” said the MEP Catherine Bearder. “This is not the future I want for my great country. I want us at the top tables of the EU – not on the naughty step waiting for permission to speak.”

The prime minister promised a “robust” response when pressed on the clause by the veteran Eurosceptic Bill Cash at parliamentary questions.

Though they propose very different ways of dealing with the challenge, the anger of British politicians contrasts with a widespread view among independent commentators that the UK will have little choice but to acquiesce to the innocuous-looking footnote on the last page of Barnier’s position paper.

“Whilst on its face this appears to be rather draconian,” said Alexi Dimitriou, an EU and competition lawyer at the law firm Ashurst, “the proposal comes as no surprise given how long [European court] judgments can take and given that there needs to be some form of effective enforcement of the rules during the transition period.”

It was a line amplified by Barnier’s senior adviser Stefaan De Rynck. “Foreseeing [the] possibility of sanctions for foul play is of course part of any agreement,” he wrote. “Why do some observers seem to assume the UK will breach rules?”

It does not mean there won’t be a fight, given that the detail and tone of the EU policy paper is so incendiary for many UK politicians.

“What stands out,” added Dimitriou, “is the non-reciprocal nature of the proposal; it is not clear what equivalent rights the UK would have if it considers that the EU is in breach of the UK’s transitional rights. No doubt this will form part of the next stage of the negotiations.”

But with just 30 working days left for agreement before the next crunch summit meeting in March, the danger is that the mounting list of British transition objections merely serves to hinder the process of moving on to future relations and securing a Brexit that all can agree on.

Those, like the Lib Dems, who wish to see a second referendum instead are emboldened by the current disarray and rancour. But those, like Rees-Mogg and Farage, who wish to see Britain walk away from talks rather than sacrifice any more independence to Brussels, have also had their best day in months.

While the new Brussels punishment clause may have been drafted with little more intent than protecting the integrity and stability of the EU, it also risks undermining the delicate coalition that has so far kept Britain largely dancing to its tune on the broader direction of talks.