Whitehall has confirmed the second batch of files tied to Lord Peter Mandelson’s controversial tenure as UK ambassador to the United States will not appear this month, marking the latest in a series of setbacks for public disclosure.

Sources within the Cabinet Office said the decision followed fresh legal advice warning that premature disclosure could trigger fresh litigation. A senior civil servant, speaking on condition of anonymity, called the delay 'regrettable but necessary' to avoid 'unnecessary exposure to legal risk.'

The announcement arrives less than two weeks after the High Court ruled that the government had acted unlawfully by failing to release documents related to Mandelson’s appointment in a timely manner. In that judgment, Mr Justice Fraser criticized the 'lack of urgency' and ordered expedited review of all remaining files.

Campaigners argue the delays are part of a broader pattern of opacity from an administration that has repeatedly cited 'national security' to block scrutiny of its diplomatic appointments. 'This isn’t just about Mandelson—it’s about whether the public can trust the government to be transparent,' said Jane Holloway, director of the watchdog group Transparency Watch.

Mandelson, a former European Commissioner and close ally of former Prime Minister Tony Blair, faced intense scrutiny during his time in Washington for alleged conflicts of interest. While the first batch—heavily redacted—revealed little beyond routine diplomatic correspondence, unredacted versions are expected to include details of meetings with corporate lobbyists and private equity figures.

The Foreign Office has not disclosed whether the new delay will push back the June target for the third and final tranche. A spokesperson declined to comment on whether Mandelson himself had been consulted on the timing of the releases, stating only that 'robust processes' were being followed.

1. First — The government missed its own March 15 deadline for the second tranche, citing 'additional legal advice.'
2. Second — The High Court ruled on February 28 that the government had failed to comply with transparency obligations.
3. Third — Campaigners have vowed to take the case back to court if the June target is not met.

In a related development, the Information Commissioner’s Office has opened a preliminary inquiry into whether the Cabinet Office breached its statutory duties under the Freedom of Information Act by withholding documents without sufficient justification.

The unfolding saga underscores broader concerns about declining transparency in Whitehall, with watchdogs warning that the Mandelson case could set a precedent for future diplomatic appointments and the release of politically sensitive documents.