PRESS ASSOCIATION -- The new Commons expenses watchdog is refusing to name MPs under investigation for dubious claims because it would be "unfair".

The Independent Parliamentary Standards Authority (Ipsa), which was brought in to clean up the discredited system, initially indicated that politicians would be identified when a formal probe was launched. It also suggested there would be a "presumption" for hearings with MPs to be held in public.

However, the body's compliance officer Luke March has now insisted that details will not be disclosed until his inquiries conclude. If the MP is eventually cleared, there will be no official confirmation that they ever faced an allegation.

The shift, disclosed by Mr March following questions from the Press Association, raises the prospect of the new regime being less transparent than its predecessor.

Ipsa chairman Sir Ian Kennedy told MPs earlier this year that preliminary investigations had been launched into 40 politicians' expenses claims since the general election.

The compliance officer's guidelines state that a substantive probe begins when there is "reason to believe that the MP may have been paid an amount under the scheme that should not have been allowed". At that point he is meant to reveal the name of the MP involved and "particulars of the matter that is to be investigated".

However, Mr March - who took over from interim officer Alan Lockwood last month - said that although a number of substantive cases are under way he is determined to have the guidelines rewritten.

"The reason why I am not (publishing) now is that we are doing this all for the first time," he said.

"One of the things that makes me nervous is the lack of proportionality. Compared to the previous world some of the things we are looking at are relatively small. But the system does not make any distinction between major problems and trivial mistakes."

Mr March said many of the allegations concern data entry mistakes by the MP or Ipsa.