The former adviser to the cabinet minister in charge of leaving the European Union has launched an online tirade against the team behind Brexit and the claims of Boris Johnson.

James Chapman, who was a former chief of staff to David Davis, says Brexit is a catastrophe and Johnson and other Leave campaigners should face jail for the claims they made about there being an an extra £350m for the NHS, should Britain leave the EU.

In a series of tweets, he asked culture secretary Karen Bradley if she could "confirm all US broadcasters are moving out of London because of the PM's deranged hard Brexit".

He also tweeted to health secretary Jeremy Hunt, the health secretary, over how British tourists could get emergency healthcare in the EU.

But in a dig at the current foreign secretary, he wrote: "Let's be honest, if we had an effective electoral law leading Brexiteers would now be in jail. #wheresmy350maweekboris."

After the tweets in which he called for a new party to be set up called the Democrats, Chapman told the Guardian the "clock is ticking" on leaving the European Union with key politicians feeling "paralysed" and "terrified of being called saboteurs, wreckers and people defying the 'will of the people'".

He also said the UK could still stay in the single market, telling the paper after he sent the tweets: "There is going to be an issue with leaving the European Economic Area. There is a separate trigger for that, which is article 127, which will have to be considered next March. There is no majority in parliament for leaving the EEA, so the government is going to have to shift its position.

"We don't have to leave it and therefore there will be no cliff edge. We'll carry on paying in and immigration is falling any way because of Brexit."

Meanwhile,it emerged on Wednesday (9 August) that Gina Miller who legally challenged the government over Brexit, says she is afraid to leave her home after getting threats of acid attacks for months.

"I have been getting threats of having acid thrown in my face for months and months now. When I see someone walk towards me on the street with a bottle of water or something, I just freak out," she told Verdict magazine.