The Financial Services Compensation Scheme has instructed Deloitte to help with its "more complex" consumer claims in a three-year contract worth £19m.
The lifeboat body said the professional services network was the only firm in the market which has the "capability, expertise and sufficiently experienced staff" necessary to meet its requirements.
Deloitte has been drafted in to help with more complex claims at the service and will be responsible for checking and monitoring evidence and gathering information from third parties including customers, providers, regulators and claims management companies.
The company will also determine the eligibility of consumers, the validity of their claims and calculate any compensation.
The FSCS said: "Processing and assessing complex pension claims made to FSCS is a technical endeavour requiring a unique set of knowledge and skills. It is not simply an administrative or claim-handling exercise."
An FSCS spokeswoman told FTAdviser: "In 2018 FSCS appointed a transformational partner for our claims processing services, however we have identified that we require specific support in processing some of our most complex claims and require increased contingency.
"FSCS needs the ability to deal with a volatile financial services market with unforeseeable events impacting the claims types, volumes, and complexity since our previous procurement."
The lifeboat body said the "complex and bespoke" nature of its service, and the vulnerable nature of its customer base, meant a particularly experienced and skilled cohort of staff was essential.
The FSCS claimed training staff to this standard at any other provider other than Deloitte could take "between 12 to 18 months" and so risked longer waiting times for consumers.
At the end of 2019 the compensation scheme pointed to an increasing number of complex and costly pension advice claims as cause for an additional £46m bill added to the adviser levy.
Earlier this year the FSCS outlined initial forecasts for its 2020-21 levy, with the overall bill estimated to come in at £635m, a jump of £87m on the total for 2019-20. This increase was also primarily attributed to a rise in the number of self-invested personal pension claims.
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