Sesame has blamed claims management companies (CMCs) for a near-100% rise in the number of complaints against it being referred to the Financial Ombudsman Service (FOS).
The UK's largest network had the most complaints of any advisory business referred to the FOS in the second half of last year, figures show - a total of 140, which was up on the 76 recorded in the first half.
More than 60 complaints were on pensions decumulation, with 37 on mortgages and home finance.
Sesame spokesman Jared Aitken said the claims represented "a tiny proportion of the business" Sesame writes annually and blamed the activities of CMCs for the rise.
"We have found CMCs are behind many of the referrals to FOS, with cases referred regardless of the merits of the complaint," he added.
"Furthermore, FOS doesn't have jurisdiction on about a third of the Sesame cases that go to them, either because the case does not relate to Sesame or the product being complained about is not regulated."
The number of complaints against Sesame found in favour of the client by the FOS was 36% in the period, well below the industry average of 72%, Aitken said.
Other advisory businesses listed included Openwork, which received 116 complaints, Positive Solutions (60), St James's Place (50), Personal Touch (47), and AWD Chase de Vere (38). Barclays received the most complaints of all financial services businesses in H2 2011, with 11,524.
Towry received less than 30 complaints, a ten-fold decrease since the 349 complaints referred in H2 2010.
Apart from the efforts of CMCs, AWD spokesman Patrick Connolly said a number of complaints against advisory firms were as a result of claims on legacy products "working their way through the system".
"We were only just above the threshold for being included on the list, and we hope we won't be included in six months' time," he said.
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