Complaints commissioner Antony Townsend said the FCA and the Fos should discuss this issue after handling a complaint from a firm which was being investigated by the regulator over its investment business shortly before an ombudsman looked into a complaint against it.
The firm said the FCA had "illegally influenced" the Fos and its handling of the complaint after it found the regulator had received a copy of the ombudsman's preliminary decision and several high-level meetings had taken place between the two organisations where the firm and complaint had been discussed.
Mr Townsend said he was unable to uphold the complaint because there was no clear evidence that the FCA had any "improper influence".
But at the same time he was unable to endorse the regulator's claim the interactions between the two bodies had been proper for the same reasons.
After reviewing the material involved he said it was hard to draw any firm conclusions, saying that unless it was decided that any interaction between the regulator and the ombudsman during a live case was improper then were would inevitably be grey areas.
He said: "I find the absence of a contemporaneous documentary explanation of the FCA’s purpose in sharing the information unsatisfactory.
"I have concerns about the apparent absence of published information about how and in what circumstances information about live ombudsman cases may be shared between the Fos and the FCA, coupled with the apparent absence of information in this particular case about any limitations on the use of that information, bearing in mind the fact that, as described above, more than one set of processes were in train.
"In the light of the points which I have made, I invite the FCA to consider discussing with the Fos whether there should be clear guidance about the circumstances in which information may be shared between the Fos and the FCA in advance of final ombudsman decisions, and about any limitations on information sharing between the two bodies, or within them; and whether, where the FCA is sharing information with the Fos, the norm should be that this will be made known to the parties, the reasons for any exceptions being recorded."
From January 2014, the FCA and the firm had been in "protracted and often contentious discussions" arising from the regulatory's concerns about the firm's approach to elements of its investment business, and whether or not the firm should restrict its activities.
Later that year the Fos upheld a complaint against the firm in matters which were "directly relevant" to those which the FCA was discussing with the business.
The firm then threatened a judicial review of this decision and an agreement was reached that the matter would be reconsidered by a different ombudsman.
Several months later, the FCA began an enforcement investigation into the business but discontinued this in 2015 to focus its efforts on two individuals within the firm instead.
In June 2015 the Fos issued a new provisional decision rejecting the complaint, but nearly a year later it issued a second provisional decision finding in favour of the complainant and the FCA investigation into the individuals was discontinued shortly after.
Eventually, in February 2017, a third ombudsman issued his decision, upholding the complaint against the firm.
Between the second and third Fos decision, the firm got hold of documents under the Freedom of Information Act which showed there had been correspondence and meetings between the ombudsman and the regulator where the issue had been discussed.
They also showed the FCA had received a preliminary decision from the Fos.
In response to Mr Townsend's ruling, the FCA said: "The FCA notes the Commissioner's decision not to uphold the complaint.
"We also note that the Commissioner has invited the FCA to discuss with the Fos whether there should be clear guidance about the circumstances in which information may be shared between the Fos and the FCA in advance of final ombudsman decisions.
"We will consider this in conjunction with the Fos."
