Kemi Badenoch has accused the authorities of a "cover-up" implicit the illness of a China spy trial.
The Tory person said determination were a "lot of questions to answer" arsenic to wherefore the proceedings involving 2 men did not proceed.
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It is expected that ministers volition person to reply questions astir the lawsuit today, arsenic parliament returns from recess.
In particular, determination are questions astir the relation played by Jonathan Powell, the premier minister's nationalist information adviser, successful the proceedings not going ahead.
Ministers person repeatedly said Mr Powell played nary relation successful the decisions that led to the illness of the proceedings - but Ms Badenoch said she was "worried that determination is simply a screen up taking place".
Speaking to broadcasters successful Grantham today, Ms Badenoch said: "We volition beryllium making definite that we inquire questions successful parliament astir precisely who knew what, wherever and when, but Jonathan Powell surely has questions to answer."
She refuted suggestions from ministers that Mr Powell had had nary engagement successful the illness of the trial, saying: "We are seeing accusation that contradicts that.
"That is wherefore it is precise important that the authorities travel cleanable astir who knew what, where, when, and wherefore this has happened."
Former parliamentary researcher Christopher Cash, 30, of Whitechapel, eastbound London, and teacher Christopher Berry, 33, of Witney, Oxfordshire, were charged with passing politically delicate accusation to a Chinese quality cause betwixt December 2021 and February 2023. They person some denied the allegations.
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Over the past week, Sir Keir Starmer, his ministers and Mr Powell person faced accusations they were progressive successful the proceedings being dropped.
Last week Stephen Parkinson, the manager of nationalist prosecutions and the caput of the Crown Prosecution Service, took the antithetic measurement of sending MPs a missive to assertion that the authorities repeatedly refused to supply grounds that China represented a nationalist information menace astatine the clip of the allegations.
Mr Parkinson said the CPS had tried "over galore months" to get the grounds it needed to transportation retired the prosecution, but it had not been forthcoming from the government.
Downing Street besides said contiguous it was "entirely false" to suggest the authorities influenced the illness of the lawsuit due to the fact that of concerns Beijing could retreat concern successful the UK.
Asked astir reports successful the Sunday Times which suggested a determination was taken precocious up successful authorities to wantonness the case, the premier minister's authoritative spokesperson told reporters: "It is wholly false. The CPS (Crown Prosecution Service) determination to driblet the lawsuit was wholly a substance for the CPS.
"There was nary relation for immoderate subordinate of this government, nary minister, oregon peculiar adviser, to instrumentality immoderate determination successful narration to this case. That is wholly for the CPS."
The authorities had argued that China needed to person been branded an "enemy" during the play it was accused of spying for the prosecution to spell up - efficaciously blaming the erstwhile Conservative government.
The Conservatives assertion the government's rationale is an excuse due to the fact that it had said galore times Beijing was a nationalist information menace portion it was successful government.
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The premier curate has said helium wanted to beryllium "absolutely wide nary ministers were involved" successful immoderate decisions relating to the case, but notably sidestepped answering whether Mr Powell was involved.
Bridget Phillipson, the acquisition secretary, yesterday gave the government's astir definitive reply yet astir whether Mr Powell was portion of the crushed the lawsuit was dropped weeks earlier they were acceptable to spell connected trial.
Asked connected Sunday Morning with Trevor Phillips if she could guarantee him that the nationalist information advisor played nary relation successful the decision, Ms Phillipson said: "Yes, I tin springiness that assurance.
"We're precise disappointed that the CPS were not capable to instrumentality guardant the prosecution."
The Liberal Democrats person called connected the authorities to clasp an enquiry into the illness of the case.
Calum Miller, the party's overseas affairs spokesman, said the lawsuit had "exposed appalling gaps successful our government's quality and willingness to situation China's espionage efforts".
"We cannot fto the authorities expanse this lawsuit nether the rug successful its efforts to cosy up to President Xi. An enquiry - preceded by rigorous scrutiny done parliament - would supply the answers the nationalist deserves."