Sir Keir Starmer has been slammed for "withholding" documents connected to the Peter Mandelson vetting probe.
The Intelligence and Security Committee (ISC) said the Government was redacting information "far too broadly".
While some redactions were previously agreed on between No10 and the committee, Downing Street's headache from the inquiry into the disgraced peer has persisted.
The committee has called on No10 that such redactions were made "in the spirit of the Humble Address".
In a statement today, the committee said: "Having seen how government is applying redactions... the committee has made clear that, in its view, they are being applied far too broadly - particularly in the case of personal information.
"We note that no body has been commissioned to review those redactions and assure Parliament that they are within the spirit of the Humble Address."
MPs on the committee also raised concerns over specific documents being "withheld" from scrutiny.
"The prime example is a vetting file held by UK Security Vetting," the statement read.
Information about Lord Mandelson's vetting was being redacted 'far too broadly', the committee said
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It continued: "The committee has made clear that it does not consider that the terms of the Humble Address allow for any documents to be withheld from Parliament: while Government may believe that there is good reason to withhold certain documents, it does not currently have the authority to so do.
"The committee has therefore advised Government that we believe it must return to Parliament to seek Parliament’s agreement to withhold any documents."
The MPs pointed to the extensive use of informal methods of communication for policy formulation, specifically WhatsApp.
"Government systems exist for a reason and should be the proper forum for the conduct of government business," it said.
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Sir Keir Starmer's Government has been accused of withholding documents
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"The committee has raised this issue before - with the last Government - and it is disappointing to see not only that it continues, but the extent to which it has spread."
Further along in its list slamming Sir Keir's team, the committee lamented the lack of "adherence to professional practices".
They labelled it "appalling" and warned it could put Britain's national security "at risk".
The Humble Address, made back in February, demanded the release of documents related to Lord Mandelson's vetting process.
Whitehall confirmed the papers would be released but "commercially sensitive" information would be hidden.
Private information, such as contact details and personal addresses, would also be hidden from public viewing.
Shadow Chancellor of the Duchy of Lancaster, Alex Burghart, has since accused Labour of conducting a "cover up".
The statement made by the ISC has since been deleted.
GB News has approached No10 for comment.