A group of MPs appointed by Commons Speaker John Bercow to assist with parliamentary duties could see their maximum pay cut amid questions about how much work they do.
Some 36 politicians from across parties serve on the Panel of Chairs, chairing debates in Westminster Hall and overseeing Public Bill and General committees.
The posts attract a salary supplement of up to £15,000 a year, depending on how long individuals have been on the panel.
But the Independent Parliamentary Standards Authority (Ipsa) has now suggested making the pay flat rate, and reducing the maximum to £9,600.
The watchdog set out the move as its "favoured" option in a consultation paper.
The document said dividing the current payroll bill of around £345,000 between the number of MPs on the panel would mean the change was "cost-neutral".
"If we assume that there will continue to be 36 members of the panel, for example, then the new salary for each member would be about £9,600 per year," the paper said.
"This would involve no overall additional cost, on the assumption that the House of Commons appoints no more than 36 MPs to the Panel of Chairs, as currently. This is the option we favour on the basis that it is cost-neutral."
The watchdog said there was "some evidence that the normal workload of members of the panel is less than that of chairs of Select Committees" who also receive a £15,025 pay supplement.
Last year, there were seven panel members who did not chair any Public Bill Committees, according to the consultation.
"Unlike Select Committees, members of the panel often share the chairmanship of a Public Bill Committee with another MP who also sits on the panel so that two members of the panel each preside over half the total sittings of a committee in one parliamentary session," the watchdog said.
"There is no minimum number of occasions on which a chair must preside over a committee that they are appointed to.
"In the 2014-15 parliamentary session, on average, members of the panel chaired half of the sittings of committees to which they were appointed, reflecting in part the 15 committees with two or more members of the panel appointed as chair.
"There were seven members of the panel who did not chair any Public Bill Committees in that parliamentary session.
"In 2014-15, General Committees sat on 234 separate occasions, and the average time it took to chair a General Committee was 20 minutes.
"There were 38 Westminster Hall debates on average in each of the nine months of the session, and debates lasted an average of 90 minutes."
According to figures in the document, introducing a single pay rate of £9,600 would mean a cut for 17 MPs who have five years’ service or more and currently earn £15,025. Another three who have been members for between three and five years would also see a reduction from £11,419.
However, 14 MPs who have been on the panel less than a year would receive an increase from £3,000. Two members of the panel are not paid additional salaries because they also chair select committees.
The panel came under fire recently when it emerged that the Speaker's official Commons account had been used to fund thousands of pounds worth of dinners and receptions for the members.
Deputy Speaker Lindsay Hoyle, who oversees the panel, had previously suggested that MPs should serve a short probationary period before being placed on the top-tier salary.
However, Ipsa said it opposed the idea as it was "not standard practice to pay individuals on probation a lesser rate of pay than others who are doing the same job".
It also highlighted that putting all members on the top rate would increase the pay bill by 56% to around £571,000 a year.
The consultation said the watchdog did not want to change the arrangements for paying select committee chairs, describing the current level of £15,025 as "appropriate".
It suggested increases could be linked to average weekly public earnings in future, in the same way as MPs' main salaries.
Ipsa recently confirmed that politicians will get a 1.3% rise from next month, busting the 1% public sector pay cap again less than a year after they received a 10% backdated hike.