Allies of Jeremy Corbyn have been accused of a dirty tricks campaign to undermine his Labour leadership rival Owen Smith.

Mr Smith was forced to repeatedly defend his past as a lobbyist for pharmaceutical company Pfizer on Wednesday as old comments he made while in the job resurfaced.

In 2005, he appeared to endorse a Pfizer-backed report offering NHS patients easier access to private-sector healthcare, writing that “we believe that choice is a good thing” in a press release.