Tony Blair's decision to inject some grit into Labour's stage-managed election campaign backfired unexpectedly last night when he suffered an embarrassing mauling at the hands of Jeremy Paxman, the BBC's famously robust Newsnight presenter.

The prime minister was asked 20 times whether he knew how many failed asylum seekers were in the country but was unable to provide a figure. He appeared to come off worse in the combative exchange on an issue where Labour is perceived as weaker than the Conservatives.