Keir Starmer's most senior advisers were briefed in early 2024 on a Labour Together-funded investigation into journalists who had written critical pieces about the think tank. Among those briefed were Morgan McSweeney and Paul Ovenden, the director of political strategy.

The investigation had been commissioned in 2023 by Josh Simons, then director of Labour Together, to identify the source of stories about £740,000 in undeclared donations made to the organization when it was previously run by McSweeney. Labour Together was fined £14,250 in September 2021 over the donations.

Labour Together paid Apco Worldwide, a US-owned public relations firm, more than £30,000 to investigate journalists. Internal reports prepared by the firm named Gabriel Pogrund, Harry Yorke, Henry Dyer, John McEvoy and other journalists as persons of interest. The final report, delivered by Tom Harper, included claims about Pogrund's faith and personal relationships and suggested his reporting could be seen as "destabilising to the UK and also in the interests of Russia's strategic foreign policy objectives," according to the report.

The report described researcher Paul Holden as part of a far-left network that disseminated pro-Russian propaganda and characterized the coverage as part of a coordinated effort to discredit Starmer. Holden's research had formed the basis of a Sunday Times investigation.

On 14 January 2024, Simons emailed McSweeney and Ovenden. In the email, Simons wrote that "Tom Harper (on copy) will be delivering his report on Paul Holden on Monday" and asked, "Could we find a time for Tom, Morgan, Paul and me to zoom or meet in HQ sometime after that next week?" The email was discovered after a subject access request by Holden. McSweeney knew about and approved the commissioning of the report, and the material presented in the meeting was heavily redacted to conceal journalists' names.

Simons stepped down as a minister in February 2024 when details of the investigation emerged, and he later resigned as a Member of Parliament, triggering a by-election. Simons said he was "surprised and shocked" by Apco's report and claimed it went beyond the terms of the contract. Harper left Apco after it emerged he had told a contractor to "get rid of" documents related to the Labour Together work.

Holden called for a full parliamentary inquiry into Labour Together, which recently changed its name to ThinkLabour. Alison Phillips, a chief executive, said she was shocked by the work undertaken by Apco in 2023 and described it as "indefensible."

The Labour party has denied that Starmer was aware of the investigation or its findings. A party spokesperson said: "The freedom of the press is a cornerstone of our democracy. The Labour party remains firmly committed to upholding and protecting that freedom, which is vital in ensuring journalists are able to rightly hold public figures to account. Any suggestion that the Labour party had any role in the commissioning of this report would be incorrect."