The number of UK defined benefit pension schemes using fiduciary management rose by 9% over the 12 months leading up to June this year the lowest increase recorded since 2008.
That is the headline finding of a decade-long study by KPMG, which also shows that growth in the fiduciary market has fallen sharply from a 30% increase observed in 2016/17.
This comes after the Competition and Markets Authority (CMA) proposed new rules for selecting fiduciary managers earlier this year, with the changes to be confirmed next March.
KPMG's head of fiduciary management research, Anthony Webb, said pension scheme trustees had adopted a "wait and see" approach in preparation for the CMA's final report.
But he added: "It now seems likely that fiduciary managers will not significantly change their investment offering to pension schemes as a consequence of the review.
"So this year may represent a blip rather than a signal for lower growth rates in the long term."
The research also reveals a small rise in the number of schemes seeking independent oversight of their fiduciary arrangements, increasing from 19% to 21%.
Oversight for new appointments increased from 60% to 66%, although KPMG warned that most schemes still do not fully integrate independent advice in their ongoing operations.
It was also found that 58% of pension schemes now show some environmental, social and corporate governance (ESG) engagement between fiduciary managers and trustees.
However, the remaining 42% have had no formal engagement on ESG over the past year - representing approximately 350 schemes.
KPMG's assistance head of fiduciary management research, Faye Mullen, said trustees would come under more scrutiny after the government published new ESG requirements in June.
"Trustees will be encouraged to demonstrate greater ESG engagement in future, and we look forward to seeing how fiduciary managers help their clients tackle this," she added.