A Conservative MP is preparing to defect from the EU Leave campaign following its claims that staying in the bloc will harm the NHS.

In a major blow for the Leave campaign, Sarah Wollaston will say on Thursday that she now backs the case for staying in the EU, senior sources said.

The GP is expected to say that Leave's central claims about a Brexit boosting the NHS are wrong and have convinced her to back the Remain campaign.

On Twitter, the MP said she believed that the NHS would be safer if the UK remained a member of the European Union.