Keir Starmer's national security chief has been accused of being too close to China following allegations over his involvement in the collapse of a Chinese spy trial.
Jonathan Powell is facing scrutiny across the political divide after he reportedly refused to call Beijing an 'enemy' of the UK in evidence for the case against a parliamentary researcher and a business consultant.
Christopher Cash, 30, from Whitechapel, east London, and Christopher Berry, 33, of Witney, Oxfordshire, were each charged with the offence of spying under the Official Secrets Act. They both denied the charges.
They were set to face trial this month, but proceedings against them were stopped after the Crown Prosecution Service said it could 'no longer proceed to trial' due to a lack of evidence, sparking criticism from Downing Street and MPs.
Government sources have stressed Powell did not have any decision-making role in the case following allegations that he met with top Whitehall officials to discuss the trial and how China would be presented.
But his relationship with Beijing has been put under the spotlight, with Cabinet Ministers reportedly fearing that his close ties could make his position unsustainable.
One cabinet minister voiced concerns that Powell is too soft on China and the UK's strategic approach towards the country 'is a little bit fuzzy' under his leadership.
Another said Powell had become a lightning rod for those criticising the government's stance on China and suggested he needed to be replaced.
'It feels difficult for him to carry on,' the minister told The Times, adding that the Government will face increased scrutiny if he remains in place.
A third added: '[Powell] thinks you can ride both horses, that you can have the economic benefits of the relationship with China while managing the security risk.
'You can't and he's wrong. They are completely entwined because China takes a whole state approach. It isn't sustainable.'
Powell began facing scrutiny after it emerged that he was allegedly included in a meeting with top Whitehall officials to discuss the trial and how China would be presented.
The meeting is said to have included Jonathan Powell, the UK's national security adviser, and Sir Oliver Robbins, the permanent secretary at the Foreign Office.
According to the Sunday Times, Powell is said to have told attendees of the meeting that Matthew Collins, the deputy national security adviser set to give evidence for the prosecution, would not describe China as an enemy, but rather as a 'challenge'.
This term has its roots in the National Security Strategy 2025 report, a document that sets out the major security risks the UK faces. However, prosecutions under the Official Secrets Act require proof that defendants acted in the interests of an enemy.
However, a spokesperson for the Cabinet Office told the Daily Mail: 'This is completely false. There has been no material change provided by the government, nor were any of the witnesses limited in the sources upon which evidence could be based.'
Downing Street has confirmed that Powell will appear before senior MPs and peers to face questions in Parliament about the Chinese spying case.
But his appearance before the Joint Committee on the National Security Strategy will be in private - even though his predecessors have given evidence to the same committee in public.
The decision by Labour ministers - who had previously claimed Mr Powell should not appear at all because he is a special adviser rather than an official - means the public will not hear his response to the allegations that he was involved in top-secret discussions that led to the collapse of the case.
Former defence secretary Sir Gavin Williamson, who sits on the joint committee which will question Mr Powell in private, told the Daily Mail: 'With such a high level of public interest in this case, it would be beneficial for Mr Powell and for Parliament for him to set out quite clearly his involvement or non-involvement.
'There's an ability for part of the session to be in private and part in public. I think he has whole series of questions he's got to answer.'
But he added that a minister should also provide a statement to the Commons about the case, on the first day back after the conference recess. 'There's a lot of people who have a lot of questions,' Sir Gavin said.
Commons speaker Sir Lindsay Hoyle is considering bringing a private prosecution against Cash, 30, and Berry, 33, after the espionage charges against them under the Official Secrets Act were dropped.
However, the Daily Mail has learnt that any private prosecution is unlikely to succeed because the Director of Public Prosecutions Sir Stephen Parkinson can take over a case and discontinue proceedings if it does not meet the Code for Crown Prosecutors 'evidential test'.
This means that the suspects are unlikely to face any further prosecution over the same issue after Sir Stephen halted the case last month.
It has emerged that Scotland Yard also has no plans to pursue the pair for any other offences including lesser crimes such as a breach of data protection rules.
Senior Tory MP Alex Burghart told the Daily Mail: 'Thanks to Labour, two alleged Chinese spies may never be prosecuted. In their desperation to cosy up to China, the Government have put our democracy and our country in danger.
'Now we hear Starmer's national security adviser will appear before Parliament - but only in private. Why won't Labour be open with the public?'
Another leading Tory said that Sir Keir himself had questions to answer over the collapse of the case and the involvement of his national security adviser and Foreign Office mandarin Sir Olly Robbins in the discussions over whether China could be called an enemy.
Shadow home secretary Chris Philp told a Politico event at the Conservative Party conference: 'Apparently, that was an instruction given by Olly Robbins and by Jonathan Powell.'
'I can't imagine Jonathan Powell, who's one of Keir Starmer's closest and most senior advisers, would have done that without discussing it with the PM first, so Keir Starmer has some very serious questions to personally answer.'
The Home Office and domestic security agency MI5 wanted the case to go ahead but the Foreign Office feared it would damage relations with China at a time when Labour is trying to rebuild links and boost trade, it has been reported.
Downing Street insisted the decision to drop the case had been taken solely by the CPS 'entirely independently of the Government'.
It is understood the Government's evidence in the case related to the period when the Conservatives were in power, during which ministers declined to call China an enemy.