Boris Johnson has warned Theresa May that the Government must make a public commitment to giving the NHS an extra £100million a week after Brexit if the Tories are to beat Jeremy Corbyn at the next election.

The Foreign Secretary believes that the Government must adopt the flagship Vote Leave pledge and spend £5.2billion a year that would have been paid into Brussels on the health service instead.

His intervention comes as hospitals struggle to cope with the winter flu crisis amid an ongoing row between the Government and NHS England over funding.

Mr Corbyn, the Labour leader, has put the issue at the forefront of his campaigning. Mr Johnson is likely to have the support of Michael Gove, the Environment Secretary and leading Leave campaigner, alongside senior Eurosceptic Tory MPs as he makes his case for the commitment.