Labour is failing to provide a "powerful, credible opposition" to the Conservative government under Jeremy Corbyn, leadership challenger Owen Smith has claimed as the two men clashed in the first head-to-head debate of the campaign.

But Mr Corbyn hit back, blaming Mr Smith and others for undermining party unity when they quit the shadow cabinet in protest at his leadership.

The challenger was booed and heckled by Corbyn supporters at the televised debate in Cardiff as he denied being part of a "coup" to oust the veteran left-winger.

But he accused Mr Corbyn of “sloganising” rather than developing effective policies and said that Labour would only have a chance of winning if it changed leader.

“I think I’m the person who’s got the energy in the debate and I think I see very clearly that we’ve not been what we need to be in recent months – which is a powerful, credible opposition to the Tory Party,” said Mr Smith. “They are riding roughshod over us.”

Party ‘disunity’

But addressing Mr Smith, Mr Corbyn said: “What I don’t understand is how you can complain about disunity in the party when you and others are the ones who resigned from the shadow cabinet at the very point when we could have taken it to them.”

The audience erupted into loud cheers at the Labour leader’s remarks, but were met with fury from Mr Smith.

In reply the Pontypridd MP said: "Jeremy, I'm not having that because you know, you know Jeremy that I wasn't part of any coup in the Labour Party."

However, his remarks were almost drowned out with boos by the audience, and the presenter had to step in.

For much of the debate, the two contenders traded promises to fight austerity, boost employment and offer protections to workers.

The pair clashed as Mr Smith acknowledged that “we agree about so much of this stuff”, with Mr Corbyn swiftly retorting: “So why did you resign?”

Mr Smith replied: “Because I don’t think you’re going to be able to deliver it. I don’t think we can win Jeremy at the moment.”

Looking at his challenger, Mr Corbyn responded: “You walked away. You walked away.”

There were clear divisions over Labour’s approach to Brexit, with Mr Smith leaving little doubt that he blames Mr Corbyn for his lacklustre campaigning in the EU referendum.

Mr Corbyn’s call on the day after the poll for the withdrawal process to begin immediately had effectively “allied ourselves to the Tories” he said.

But Mr Corbyn insisted: “We spent a lot of money on it, we did a lot of campaigning. I travelled the whole country doing a very large number of meetings.”

– (PA)