The accusation comes on top of claims that No 10 staff had a party last Christmas while the country was under lockdown rules.
Downing Street has insisted no Christmas party took place at Number 10 last year despite reports.
The former special adviser said Boris Johnson showed 'appalled disbelief' when he discovered what leaving the customs union meant.
The PM's former special adviser has launched yet another scathing attack against his former boss.
Cummngs hit back at Morgan after the ex-GMB host criticised him for not allowing Tory MPs to appear on the show.
The BBC said: 'We will be taking this up with Emily.'
Here's what's on the box this evening.
Johnson is said to have concluded the email with: 'We GOTTA turn it round.'
The prime minister's former chief adviser claimed he said the health secretary was 'hopeless'.
The PM's former senior adviser has leaked a WhatsApp message in which Johnson brands health secretary Matt Hancock 'totally f***ing hopeless'.
Mike Padgham, chairman of the Independent Care Group said homes were “forgotten” as the virus first began to spread in the UK last year.
The government has revealed how many people living in care homes died after one of their residents was discharged from hospital after testing positive for COVID-19.
Cummings gave evidence about the pandemic to MPs during a marathon seven-hour session.
Here are nine remarkable claims Cummings made about Boris Johnson during his seven-hour committee appearance on Wednesday.
Government officials feared closing the UK’s borders at the beginning of the coronavirus outbreak would be seen as racist, Dominic Cummings has claimed.
ITV said Dominic Cummings will allege the prime minister made the comments last autumn.
As part of his damning evidence about the government’s response to the coronavirus pandemic, Cummings said there are 'thousands of people' who could provide better leadership.
'There is no plan.'
Dominic Cummings accused the health secretary of lying to cabinet colleagues.
Dominic Cummings made the extraordinary claim about his former boss in a damning evidence session.
Transport secretary Grant Shapps, who last spring defended Cummings’s trip to Durham, said the actions of the former chief adviser to the prime minister had weakened the message to the public.
Dominic Cummings is giving evidence about the government's response to the coronavirus pandemic, in what could be a damaging day for Boris Johnson.
Dominic Cummings will claim Boris Johnson said 'COVID is only killing 80-year-olds' ahead of the disastrous second wave, according to a report.
It's not often a House of Commons select committee meeting is one of the biggest political events of the year.
The prime minister is facing increasing pressure to answer questions about a host of controversies that have emerged in recent weeks.