Tom McPhail, head of pensions research at Hargreaves Lansdown, has cast doubts over the merits of the idea following Mr Webb's comments at the weekend.
Backers of such schemes say they offer greater value and more certainty than most current pension products, allowing workers to pool their pots and share the risks of investment.
But Mr McPhail said the danger with such CDC schemes lies with the risk controls and if they are not properly regulated or if the investments fail to perform to expectations members can find payouts being cut.
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Mr Webb was quoted by The Times as saying: "Some of the best pension schemes in the world are run on a collective basis. I would like to see British workers have access to schemes run on this basis."
Mr McPhail said, however, they do not necessarily produce higher investment.
He said: "Claims to be able to boost pension payouts at no additional cost or risk are always going to prove popular - particularly in the run up to a general election. The arguments in favour of these schemes are unproven.
"There is clear evidence both from recent Dutch experience and from our own with profits funds that such schemes can go down as well as up.
"They are complex, uncertain, unproven and rely on a constant flow of new members for their long-term sustainability."
He suggested other measures would be better to improve the pension system, such as a price cap on auto-enrolment schemes and reform of the regulations on the sale of annuities.