The parliamentary expenses watchdog was being urged to let MPs claim for mortgage interest payments again months before the "double renting" controversy broke.
The call came in responses to a survey of politicians carried out by the Independent Parliamentary Standards Authority (Ipsa) over the summer.
The research found a slight overall improvement in MPs' perception of the system.
But more than a third said it was still too complex, slow and time consuming.
Some 85% said they had opted not to claim expenses they were entitled to - with 40% admitting they were concerned about the public's reaction.
One MP wrote: "I reckon that at any one time I am subsidising Ipsa by £1,000 because of negative cash flow. It is still taking three-four weeks to pay some claims."
The annual survey was conducted before it was revealed last week that dozens of politicians have been claiming to rent a London home, while letting out their own property in the city.
Many blamed Ipsa's ban on mortgage interest claims, which came into force last month, for creating a perverse incentive to move out and rent.