Published: 2:01 PM May 16, 2019 Updated: 8:42 AM September 18, 2020

Labour's John McDonnell has said that he and Jeremy Corbyn are Remainers 'deep' in their hearts, in a last-ditch attempt to win back Remainers planning to vote in other ways at the European elections.

The shadow chancellor told the Wall Street Journal CEO Council conference in London: "Deep in my heart I'm still a Remainer."

Asked if Labour leader Corbyn was also a Remainer in his heart, the shadow chancellor responded without hesitation: "Yes."

McDonnell, however, criticised those attempting to thwart Brexit talks between the Conservatives and Labour, which includes Boris Johnson.

He said: "We have been at this five weeks, we haven't seen the significant shift yet that we require to be able to support a deal.

You may also want to watch:

"And, let's be absolutely straight, today hasn't helped. We are not near what we want.

"However, we then get a letter signed by a number of senior Conservatives, published this morning, by Boris Johnson... who is certainly going to be in contention for the leadership. Very likely to be the next leader.

"Could well be prime minister in, literally, months, and in a situation where he in his letter today says he is not going to accept a customs union and, actually, he will overturn the deal that we... negotiate.

"It gives us no security on that. And we expect a responsible government on that."

The shadow chancellor added: "Our big problem now is, if we are going to march our troops in parliament to the top of the hill to vote for a deal, and then that's overturned within weeks, I think that would be a cataclysmic act of bad faith."

Jeremy Corbyn infruriated Remainers after the local election by claiming the results showed that a Brexit deal must be done.

He explained: "I think there's a huge impetus on every MP - and they've all got that message, whether they themselves are Leave or Remain, or the people across the country - that an arrangement has to be made, a deal has to be done, parliament has to resolve this.