Labour leadership challenger Owen Smith has not held back in his latest attack on Jeremy Corbyn, warning the party is "increasingly divided" under the left-winger's watch.
"By failing to act against abuse, attacking party staff and the NEC and encouraging talk of de-selection, Jeremy has shown that he is both unwilling and unable to act as a unifying figure," Smith said.
"That's not the leadership the Labour Party needs – it's not leadership at all.
"He says he wants to build bridges, but the truth is he appears more interested in deepening the divides within the party than winning elections.
"If we are to defeat the Tories in 2020 then we need to be united against them, not divided against ourselves."
The comments come ahead of Corbyn's and Smith's clash on the BBC's Question Time show at 9pm BST tonight.
The Labour leader's camp hit back by accusing Smith, the former shadow work and pensions secretary, of "consistently" talking the party down.
"Smith's latest helping of 'Project Fear' only recycles allegations he knows to be false or misleading, but it won't wash with Labour members and supporters who want open, honest politics," a Jeremy for Labour spokesman said.
"Our campaign has set out a positive vision to rebuild and transform Britain. In contrast, Owen Smith has shown himself yet again to be the real 'disunity candidate'."
The exchange follows Corbyn's "refusal" to back the UK remaining inside the EU's single market in the wake of the historic Brexit vote.
The position puts him at odds with his close ally and shadow chancellor John McDonnell, who has warned leaving the free trade area would create "substantial" damage for the UK economy.
But despite the row, Corbyn is expected to retain his leadership on 24 September. A poll for YouGov for The Times, of more 1,000 Labour members between 25 and 29 August, put him 24 points ahead of Smith (62% versus 38%).