AJ Bell boosted its assets under administration 20% in the six months to the end of March, from £12.6bn to £15.1bn.
The number of SIPPs administered by the provider increased by 24% from 44,600 to 55,500 in the same period.
Andy Bell, chief executive of AJ Bell said SIPP numbers have benefited from the growing understanding by advisers and clients the prodcut can be used as a mainstream financial planning solution.
"Despite some adverse external influences, the SIPP market remains buoyant and the shift from traditional pension structures to low-cost SIPPs shows no signs of abating," he said.
Yesterday, AJ Bell announced it will extend its annual fund rebate on its Sippdeal platform to include SIPP accounts.
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