Advisers are to face widespread disruption on the Ascentric platform as the provider halts several services during its replatforming in November.
For two weeks from Tuesday, 13 November at 6pm advisers will be unable to perform any work on their portfolios. This applies to rebalances, money allocation, switches, updates and new models.
Advisers will also be unable to sell funds or shares from 20 November at noon until 26 November, and new wrapper set ups by cheque are not permitted for 10 days after 6pm on 16 November.
Meanwhile, new business applications, Sipp payment requests and Crest certificates must be received by Ascentric by 16 November or they will not be dealt with until the replatforming is complete on November 26.
The Royal London owned platform said its decision to prevent advisers from carrying out a wide range of functions as it replatforms was in order to avoid the mistakes made by platforms such as Aviva and Aegon.
Users of both the Aviva and Aegon platforms had experienced extensive problems with their providers after they replatformed earlier this year.
A representative of Ascentric said: "As a custodian of assets our primary duty is to migrate client details and assets safely. For this reason, we decided to restrict rebalancing on the platform in the run up to migration.
"We did so after carefully considering the interests of our clients, users and the overall impact of the migration.
"We have learnt valuable lessons from others who have migrated before us and we believe our approach is in the best interests of our end clients.
"We also consulted with large DFMs and regular users of the platform and they all agreed this was a sensible approach given the experiences they have had with other platforms who have recently migrated."
Martin Bamford, who runs Informed Choice Financial Planning in Cranleigh and is a client of Ascentric, criticised the way the provider approached its tech upgrade.
He said: "A platform that can’t facilitate rebalancing or indeed any investment trading for a number of days has failed in its primary purpose.
"Ascentric seem to be so desperate to upgrade their platform technology that they have neglected to serve their adviser customers and end investors."
He accepted it was important for platform providers to keep technology up to date, but "not at the expense of basic platform functionality for a period of weeks".
He said: "A more gradual migration of investors to the new platform could have been planned in order to address these challenges."
Ascentric already faced problems when migrating a cohort of clients to its new platform in July.
The provider is moving clients to a revamped platform in a "phased approach" in order to mitigate the challenges presented by the new technology underpinning its new platform.
In August it conceded it had taken weeks to fix the bugs which had seen some clients experience problems with receiving income payments after they were migrated.