MPs are braced for more expenses controversy as details of millions of pounds in claims from last autumn are released.
Despite objections, the material being published by the Independent Parliamentary Standards Authority (Ipsa) will include requests for reimbursement that were rejected, as well as those that were approved.
It is the second tranche of expenses the watchdog has issued since it took over administration of the system from the House of Commons authorities last May.
An Ipsa spokesman said some 25,000 claims from September and October would be available on its website from 10am. In future, information will be published in arrears every two months.
There has been criticism that, while each transaction will be listed, copies of receipts are not being published.
The disclosure could also fuel anger among MPs of all parties at the tough regime imposed by Ipsa in the wake of the damaging 2009 expenses scandal.
David Cameron has branded the arrangements “anti-family”, and warned that unless reforms are brought forward he will step in to force changes.
The watchdog is currently carrying out a consultation on proposals including giving MPs with families more money for accommodation, and has signalled restrictions could be loosened further in the longer term.
With negotiations over its future at a key stage, Ipsa has also announced that chief executive Andrew McDonald is taking sick leave. Mr McDonald was diagnosed with prostate cancer last year and will be away from his desk for around four weeks.
A statement issued by the watchdog said: “His prospects for a full recovery are good and he plans to return to his role at Ipsa in early March.”