After the European Parliament finally voted to approve the Brexit trade deal last week, you’d be forgiven for thinking the Remain campaign had packed up their placards and sold off their mailing lists to the Lib Dems.

But Parliament Square can reveal a “rejoin” campaign masterminded by Michael Heseltine and Lord Adonis has been asking for donations and lobbying MPs to reverse Brexit.

The European Movement UK, which claims to be the largest pro-European organisation in Britain, hit a snag when the ex-Tory MP Dominic Grieve accidentally emailed several eurosceptic MPs asking for their support.

The former attorney general sent — then quickly retracted — a message to bemused ERG members asking for cash to pressure MPs and to “grow our team”. It also revealed that the group had sent every MP a report which “reveal[ed] Brexit’s true damage”.

The email went on: “This is not closed-door lobbying by vested interests, but people-powered campaigning. It is down to us to expose the true scale of the harm being done by this deal and urge real change.”

Grieve attempted to correct the mistake by using Outlook’s “recall” function but tech-savvy eurosceptics were able to read the message by opening their deleted emails folder.

However not everyone was included in the error. ERG Chairman Mark Francois said:

“For some inexplicable reason, my invitation to join this nascent campaign to rejoin the EU seems to have become lost in the post.

“Nevertheless, as of this weekend, I can think of 33 million good reasons not to take these people up on their kind offer.”