Aviva's platform is still causing problems for advisers, nearly a month after its replatforming was completed.
There are still issues with the new client reporting function and there are technical issues which have affected payments for people in drawdown.
Chris Durant, a financial adviser with The Medical Partnership, said: "It is four weeks today that the platform became available and still to this day there are not client reports.
"I am seeing two high net-worth clients today and I have no reports of their pensions and investments to provide them.
"They were promised within a week and then it got delayed and delayed.
"Aviva's platform has gone from being the best to use to being the worst. It was so simple."
Mr Durant also said some of his clients had still not received money from phased drawdown for four weeks.
The platform was unavailable for six days beginning on the evening of 17 January as it moved to FNZ, its new technology provider.
But just one day after it came back online after the upgrade, investment advisers found they and their clients were locked out of the platform.
A spokesman for Aviva said: "There has been an issue with the new client reporting functionality, which has required us to restrict the service. This is now resolved and we are completing thorough testing before making this available to advisers.
"We anticipate this being available from this Friday.
"We have had a small number of technical issues, which have affected a small proportion of payments. In the majority of cases we have identified the root cause. However, a small number of cases are still being investigated.
"We are liaising with advisers to resolve cases where a customer has suffered a delayed payment and is in urgent need of income or a withdrawal."