Norwich South Labour MP Clive Lewis became the target of criticism at a mass rally held to oppose the Conservatives.
The People's Assembly Against Austerity held a protest in Birmingham, but one of its opening speakers launched a verbal attack on Labour MPs who did not support Corbyn's leadership.
John Rees, a spokesperson for the organisation, hit out at MPs who said they had no confidence in Labour leader Jeremy Corbyn, adding: 'I'll say this to Clive Lewis as well. Every pound spent on Trident.
'Every pound spent on the Nato imposed 2pc of GDP arms budget.
'Every pound spent on guns and weapons and bombs, is a pound not spent on hospitals and schools and houses and decent wages.'
He added: 'You're only there, you are only in the shadow cabinet, because Jeremy Corbyn put you there.
'So start defending Jeremy Corbyn's policy on Trident and Nato and arms spending.'
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