The wealth management firm has questioned the change and urged savers to consider their options to mitigate the adverse effects.
Nigel Green, chief executive of the deVere Group, said he was baffled by the changes.
He said: "This could wreak havoc on pension funds and I'm baffled that very few people seem to be aware of it, let alone causing a fuss about it. It appears to be slipping through almost unnoticed."
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"Changing the index from RPI to CPI will have a significant, negative effect as CPI is generally lower than RPI-usually 0.5 per cent and one per cent. This means that each year individuals with a final salary scheme will receive, say one per cent less increase in their pension payments.
"That might not sound like much but when it's compounded over years it makes a big difference."
Mr Green gave the example of a person who retires at 65 and lives until they are 85, their retirement income would be reduced by a fifth.
To lessen the effects of the change, Mr Green suggested alternative options such as consumers transferring into a defined contribution scheme such as a Sipp.

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