Sesame is facing an Financial Services Authority (FSA) complaint over allegedly negligent advice given by a member firm.
Julian Pruggmayer, an IFA at Financial Risk Management, inherited two clients from Alan Mason, an IFA at Financial Distinction and Sesame appointed representative.
The advice concerns a £60,000 investment into Arck LLP, a Cape Verde property fund whose directors are currently on bail under suspicion of fraud.
Pruggmayer said he received a verbal assurance from Chris Pike, head of compliance at Sesame, that the firm had admitted the advice was negligent, and that the network would be paying out on the claim.
However, after a two month delay, Pruggmayer said he would be writing to the FSA expressing his concerns.
In the text of a letter to Pike, he said: "Your firm still has not provided a settlement figure for us: I consider your firm has had more than enough time and this is the last correspondence we will enter into.
"All future correspondence will be with the FSA, who as I am sure you are aware have recently taken action against another firm, P3 Wealth Management, over UCIS mis-selling."
Sesame has until the middle of next week until an official complaint is made, Pruggmayer said.
In March, Arck went into liquidation, leaving investors facing up to £60m of losses. Directors Kathryn Clark and Richard Clay were arrested by Nottinghamshire Police after it evidence was found to suggest Clark may have tried to falsify statements to show Arck had £13.7 million in a bank account, which actually contained £25.90.
The FSA then cancelled the permissions of HD Administrators, a SIPP which administered the majority of investment into Arck - and which listed Clark as a director.
Financial Distinction was unavailable for comment.
A spokesperson for Sesame said: "we operate to the highest regulatory standards and take all complaints very seriously.
"Cases such as this are extremely rare and as soon as we were notified we conducted a thorough investigation, which found in favour of the two clients.
"We are currently calculating the compensation amounts and will be contacting them again shortly."
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