Former shadow chancellor Chris Leslie has launched a scathing attack on a senior member of Labour's treasury team after they refused to rule out MI5 involvement in the party's troubles.
Unite secretary general Len McCluskey suggested on Friday that intelligence services could be using “dark arts” against the current Labour leadership.
Questioned on the comments on Sky News, shadow chief secretary to the treasury Rebecca Long-Bailey refused to dismiss the theory, saying only "Given the last few months in politics, nothing would surprise me."
But speaking to City A.M. Leslie blasted the Salford and Eccles MP: "It is ludicrously embarrassing for supposedly senior people to be getting in the realms of crazy theories like this.
"We have got to get a grip and become a serious party again."
Former Labour leadership contender Angela Eagle has previously rejected McCluskey's comments, telling the Guardian: "I’ve known Len for 40 years. I worked with him and other trade unions on combating the Tories’ awful trade union bill and on stopping Sunday trading changes, and he knows I spent years working for the trade union movement. His comments are over the top."
Eagle's constituency office was attacked on the day she launched her leadership bid in an attack that was immediately condemned by Labour leader Corbyn, but today a party source accused the party's leadership of "fanning the flames of division".
"This type of conspiracy theory thinking is irresponsible and dangerous. Political leaders have an obligation to substantiate what they say. The facts matter, and it should worry every Labour member and supporter to see the leadership of our party resorting to this kind of post-truth politics," they said.
"Rather than making crass insinuations to smear their opponents, he leadership of our party should be taking on the culture of bullying, intimidation and aggression that works in their name and for their interests."