John McDonnell has invited Jeremy Corbyn critic and New Labour architect Lord Peter Mandelson for tea to talk about Brexit. The shadow chancellor extended the invitation to Mandelson after he delivered his pre-Spring Statement speech in central London on Thursday (2 March).

"[I would invite Mandeslon to] have a cup of tea and discuss issues of common concern," he told reporters. McDonnell also praised the former business secretary's recent "incredibly interesting" pro-EU speech in the House of Lords.

McDonnell made the move just two weeks after Mandelson admitted that he works "every single day" to "save" Labour from Corbyn.

"Why do you want to just walk away and pass the title deeds of this great party over to someone like Jeremy Corbyn? I don't want to, I resent it and I work every single day in some small way to bring forward the end of his tenure in office," he told a north London audience.

"Something, however small it may be – an email, a phone call or a meeting I convene – every day I try to do something to save the Labour Party from his leadership."

McDonnell also thanked author and The Guardian columnist Owen Jones for his advice to Corbyn. Jones, a former research of McDonnell's, has urged the Labour leader to "think hard" in the wake of the party's historic Copeland by-election defeat.

The shadow chancellor revealed that he had invited Jones to advise Corbyn's top team on a "regular basis", but the left-wing journalist apparently turned him down. Elsewhere, McDonnell urged Chancellor Philip Hammond to commit more money to the NHS as part of his Spring Statement.

"Based on estimates by the Chartered Institute of Public Finance and Accountancy, the NHS and social care face a funding gap of between £8.5 and £15bn by 2020," he said.

"Published figures indicate that tax receipts are currently higher than anticipated. Given that we're facing an immediate crisis in the NHS and social care, I'm calling on the Chancellor to use that money to address this NHS and social care emergency.

"Any measure less than this is likely to be inadequate. It is not just those who rely on our public services who have suffered under this government."

A Conservative spokesperson said: "Labour have today shown what a shambles they are – with the shadow chancellor suggesting a way of funding the NHS the Labour leader says won't work.

"The truth is that a strong NHS needs a strong economy, and only a Conservative government can deliver that."