Parliament’s expenses watchdog is using a procedural ruse to hide the identity of dozens of MPs who have been investigated for misusing public money.

Under rules set by the Independent Parliamentary Standards Authority (Ipsa), MPs under investigation for unjustified or fraudulent expense claims must be publicly identified.

But the organisation’s compliance officer, Peter Davis, has avoided naming individuals by carrying out detailed “assessments” of the complaints, denying they amount to formal “investigations”.

The loophole last week allowed Mr Davis to refer two MPs to the police over expenses fraud without ever launching a formal investigation, which would have triggered a public announcement.

It has also allowed other MPs to avoid publicity about using taxpayer-funded websites for party-political material by paying back website domain fees to Ipsa, or simply removing content from sites.

Peter Davis, Ipsa's compliance officer, has so far avoided naming individuals

Ipsa previously proposed conducting probes in secret to prevent “reputational damage” to MPs – but the idea was dropped after criticism from the Commons Standards Committee and Committee for Standards in Public Life. It now appears that Ipsa is using “assessments” to get around calls for transparency.

According to a breakdown of cases, released by Mr Davis’s office in response to a Freedom of Information request, 40 “assessments” of allegations against politicians were carried out in 2014-15. But just one – relating to Conservative MP Bob Blackman’s mileage claims – was classified as a formal investigation and disclosed publicly.

Among those listed as “closed prior to an investigation” was a case in June last year where an unnamed MP claimed for a taxi journey that was not allowable. The compliance office concluded it had been a “legitimate error by a member of staff” and said it had been “repaid in full”.

In another case, an allegation was made that an MP’s staff had filed duplicate claims for a hotel. Mr Davis considered the matter closed after “the MP provided a valid explanation for why two separate hotels were claimed inadvertently for the same night and... repaid”.

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The approach taken by Mr Davis means that Ipsa’s regime is less transparent than that operated by the House of Commons.

Referrals to the police at the request of parliamentary standards commissioner, Kathryn Hudson, are announced publicly. She also publishes details of cases that are “rectified” with small repayments or apologies, and information about complaints that are not upheld.

Mr Davis, a former police officer, had not revealed that MPs had been referred to the police before it was mentioned on page 74 of his 77-page annual report last week.

He defended his approach to publicity: “I am cognisant that publicity, especially in cases without foundation, carries an inherent risk of reputational damage.”

In evidence to the Standards Committee in October last year, Mr Davis indicated that he would like even less transparency, saying “the vast majority of cases can be dealt with quite effectively without the need for any publicity”.

Expenses scandal: Ipsa’s findings

Allegation: An MP’s staff engaged in non-parliamentary work during contracted hours and the constituency office was used for party activity.

Outcome: Closed prior to an investigation.

Reason: No evidence of a scheme breach.

Allegation: A letter sent by the MP to constituents contained party political messaging.

Outcome: Closed prior to an investigation.

Reason: Analysis of information showed no evidence of a scheme breach.

Allegation: Complaint that an MP owned a property and was also claiming rent for a property in London.

Outcome: Closed prior to an investigation.