The Financial Conduct Authority (FCA) has said platforms need to do more to incorporate re-registration and has issued a warning over exit fees.
It follows a thematic review of platforms' readiness for new rules set to be introduced next month.
From 6 April, platforms can only be paid via an explicit platform charge on new business.
The FCA declared itself generally pleased with firms' progress, but it has singled out re-registration as an area that requires "further progress".
"We have said and we expect firms to facilitate a transfer of investments from one platform to another within a reasonable time frame," FCA director of long-terms saving and pensions Nick Poyntz-Wright said.
"In the course of our work, we found more limited progress in this area than we would have expected. We do want firms to attend to that."
Poyntz-Wright also suggested the FCA had concerns about providers' exit charges.
"We would not want those exit charges to get to a level where they would present a barrier to exit for the customer and to inhibit competition more generally in the market," he said.
Exit fees have recently come to the fore as execution-only platforms revealed their unbundled pricing structures.
Charles Stanley Direct has already hit out at rivals' high transfer charges as being ‘anti-competitive' as it has said it will waive its own exit fees.
In terms of re-registration, a number of industry experts have warned the increasing complexity of products could lead to delays in investment transfers.
Firms are also urged to improve on their contingency plans.
Off the rails
Poyntz-Wright said: "In conducting their programmes, we saw limited evidence of firms thinking about what they would do if their particular change programme began to go off the rails.
"It is not uncommon for issues and problems to arise and we would expect firms to have a plan B to fall back on."
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Read the FCA's latest paper on platforms HERE.
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