The UK government is facing a parliamentary inquiry into its handling of Freedom of Information (FOI) requests following a court case that exposed transparency failings.

The inquiry, launched by the Public Administration and Constitutional Affairs Committee (PACAC) this Thursday, will examine whether a secretive unit in the Cabinet Office, known as the Clearing House, has broken FOI laws.

Conservative MP William Wragg, the chair of the House of Commons committee, said the inquiry was needed because “the perceived opacity of how the FOI Clearing House operates has the potential to damage trust in governance and transparency legislation. As a matter of trust, we felt it is something that must be addressed at the earliest opportunity.”

The committee pointed to a court case openDemocracy launched against the Cabinet Office in April, which demanded the release of information about how the unit deals with requests for information from journalists, campaigners and researchers.

“OpenDemocracy, who brought the case, accused the body of obstructing access to information they are entitled to seek under the FOI rules,” wrote the committee in a statement.

In his verdict, judge Chris Hughes said there was a “profound lack of transparency about the operation”, which might “extend to ministers”. He added that documents presented by Michael Gove’s department had “misled” the tribunal.

Fleur Anderson, Labour shadow minister for the Cabinet Office, raised the case in Parliament on Thursday, asking if “certain journalists or campaigners” were treated differently by the Clearing House.

Julia Lopez, a minister at the Cabinet Office, said that the “background of who is asking is not the criteria for how we treat that request”.

Earlier this year, internal emails obtained by openDemocracy revealed that information requests were flagged by staff at the Attorney General’s Office because they were submitted by openDemocracy reporter Jenna Corderoy.

Staff at the office wrote: “Just flagging that Jenna Corderoy is a journalist” and “once the response is confirmed, I’ll just need [redacted] to sign off on this before it goes out, since Jenna Corderoy is a reporter for openDemocracy”.

Under FOI law, requests are supposed to be ‘applicant-blind’, meaning who makes the request should not matter.

Press freedom campaigners have described the Clearing House as “Orwellian” and a shadow minister accused the government of “blacklisting” journalists.

In February, more than a dozen current and former national newspaper editors signed an openDemocracy public letter calling for MPs to urgently investigate.

Gove previously dismissed concerns about government secrecy, telling the PACAC in December that “the idea that there is a secret Clearing House or any sort of blacklist is ... not correct.” He is expected to be called to give evidence.

The inquiry will not extend to whether the Freedom of Information Act 2000 itself requires reforms or whether other government departments and public bodies have been complying with the legislation.

Transparency campaigners welcomed the inquiry, but said that the issues facing freedom of information “go well beyond the Cabinet Office”.

“Delays are a chronic problem often holding up the release of information for years. Enforcement of FOI has been weak,” said Maurice Frankel, director of Campaign for Freedom of Information.

“Public sector contractors are not properly covered,” he added. “The government is picking and choosing which new bodies should be subject to FOI. Government business is being conducted by text messages, which are difficult, and sometimes impossible, to obtain.”

Lord Clark, a former Labour minister and chief architect of the Freedom of Information Act, has warned that he hears “almost daily” about public bodies refusing to abide by the law.

The Information Commissioner’s Office which deals with complaints about FOI requests has had a 43% increase in cases since the start of the pandemic, according to the Campaign for Freedom of Information.

The Cabinet Office has received the highest number of complaints. The office received 7% of the FOI requests made to government departments in 2020 but accounts for 20% of ICO complaints.