The FOS is proposing to publish the information twice a year.
It is now calling for opinions on practical issues such as how best to show data for businesses that operate under various trading names, verify data on the outcome of complaints, contextualise data and what period it should cover.
The move follows recommendations in the Hunt Review that called for greater transparency in complaints-handling, including publishing publicly available information about how individual financial businesses deal with complaints.
Beachcroft Regulatory Consulting managing director Richard Hobbs says there are too many intervening variables in play for the data to be useful for consumers.
He points out that complaints about banks usually concern current problems, while complaints about investment products can go back years, altering the useful meaning of the data.
He says: “This is like comparing apples and oranges. It’s fraught with difficulty. This is a far more complex issue than just putting the information into the public domain.
“You’re acting on figures that are difficult for experts to understand, let alone consumers. And the trouble with complaints data is that you don’t damage brands, you damage a whole industry.”