JEREMY CORBYN challenged Owen Smith to back a fully public NHS yesterday after his leadership rival defended his past as a lobbyist for drug privateer Pfizer.

Mr Smith is under scrutiny over the £80,000-a-year post as “head of government affairs” for the US company, which is famous for producing sexual aid Viagra, he held between 2005 and 2008.

When he unsuccessfully stood for Parliament in 2006, he claimed privateers could bring “good ideas” and “valuable services” into the NHS without undermining its public ethos.