Kemi Badenoch has branded claims Tory leadership candidates were wrong to question the authorities over the Southport atrocity as “rubbish”.

Prime Minister Sir Keir Starmer came out fighting after being quizzed over why it took so long for Axel Rudakubana’s terrorism charge to be publicised.

Rudakubana, 18, was charged with three murders and 10 attempted murders at a Taylor Swift-themed dance class in July. On Tuesday, he was charged with a terror offence after a jihadi guide was found at his home with the poison ricin.

Sir Keir warned Tory leadership contenders: “They can either support the police in their difficult task, or they can undermine the police. I know what side I’m on.”

But Mrs Badenoch responded with “rubbish, rubbish, rubbish” as the Prime Minister spoke.

And former minister Neil O’Brien raged: “So we are not allowed to ask the PM any questions about what he knew when in the Commons, but he can say this? Absurd.”

Speaker Sir Lindsay Hoyle warned MPs should not make any reference to the Southport case in the Commons to avoid prejudicing the legal process.

He told MPs ahead of Prime Minister’s Questions: “I wish to remind the House that, following the horrendous terrible incident in Southport on July 29, a suspect is awaiting trial having been charged with multiple offences. That means the House sub judice resolution is engaged and references should not be made to the case.

“I know that all honourable members wish to see justice done in this case. It is therefore of paramount importance that nothing is said in this House which could potentially prejudice a proper trial or lead to it being abandoned.”

The UK’s terror law watchdog has declared the authorities must be more open about suspects involved in atrocities like the Southport stabbings.

Jonathan Hall KC said there is “a fair amount of information that can be put into the public domain” to avoid online conspiracy theories and disinformation spreading.

Merseyside Police said the new charges point to the Southport stabbing being a terror attack.

But the decision to charge Rudakubana with a terror offence and making a biological weapon has prompted a wave of fury, with claims of a cover-up and demands to know what the authorities knew and when.

Mr Hall, the independent reviewer of terrorism legislation, told BBC Radio 4’s Today programme: “The police and the CPS are operationally independent, and it’s important that they are, and it’s right that the Government trusts the prosecuting and the police authorities as to what might damage potential future proceedings. So I think there has to be a relationship of trust.

“And if the police and CPS are saying ‘we really don’t think that you can put any more in the public domain’, I think that the Government ought to be affected by that.

“On the other hand, I also think that the Government has to be aware, and will be aware, that if there is an information gap, particularly in the mainstream media, then there are other voices, particularly in social media, who will try and fill it.

“I would always say to the Government – and do say to the Government, as I say to the police – if there is information that you can give, put it in the public domain, and be really careful that you don’t fall into the trap of saying ‘we can only say zilch, because there are criminal proceedings’.

“Quite often, there’s a fair amount of information that can be put into the public domain, and I think I detect that the police are trying to do that. They realise now that just saying ‘there’s a charge, we can’t say anymore’, is not going to cut it these days.”

Former Prime Minister Liz Truss told TalkTV: “I would find it extraordinary that he did not know what was going on.

“These materials were found in the suspect’s house, that must have happened fairly soon after the appalling atrocity. I find it extraordinary that he wouldn’t know those things and it seems the public has not been told the truth.

“People know that’s not true. And it erodes trust in politics. It erodes trust in the machinery of Government because it’s not just the politicians we are talking about here. It is the police, it is the intelligence services. It is the CPS.”

Merseyside Police Chief Constable Serena Kennedy said at a press conference that the ricin, which can be highly toxic and is naturally derived from castor oil plants, was analysed by biological experts at Porton Down.

The terror offence relates to a computer file entitled “Military Studies in the Jihad Against the Tyrants: The Al-Qaeda Training Manual”. Ms Kennedy added: “I recognise these new charges may lead to speculation.

But she added of the Southport atrocity: “The matter for which Axel Rudakubana has been charged under the Terrorism Act does not require motive to be established.

“For a matter to be declared as a terrorist incident, motivation would need to be established.”

Tory leadership contender Robert Jenrick suggested the state may have been “lying” about what was known about the Southport attack suspect.

He demanded to know what Sir Keir was told about Rudakubana.

Mr Jenrick told ITV’s Good Morning Britain: “I want to know when the Prime Minister knew: we don’t know that information, we don’t know what the advice of the police was in this case, and we don’t know why the police has chosen not to say this.

“The effect of this has been that there has been speculation over the summer, there has been a loss of trust in the police and the criminal justice process and I think that’s wrong.

“The state should not be lying to its own citizens.”

Asked if he thought the state had indeed lied, he said: “We don’t know. We don’t know the reason why this information has been concealed.

“Why has it taken months for the police to set out basic facts about this case that it is reasonable to believe were known within hours or days of this incident occurring?”