The closed nature of 'black box' cloud offerings are not suitable for financial institutions, according to Morgan Stanley.
"If a service provider wants to sell us a black box it is not going to work [for us]," Steve Matthews, executive director at Morgan Stanley, told the 451 Research Group's HCTS conference in London today.
Matthews said that the bank would rather choose a vendor that was "open" so that it would be able to work with the supplier to develop a solution that was aligned to the bank's requirements.
For Friends First Group, another financial institution, the problem with black box cloud solutions was data security and compliance.
"Financial institutions need to see what the data is. If they can't then it is a big, big issue," said Lavinia Morris, IT manager at Friends First Group.
"I need to tell my auditors that [the data] is secure and safe. Even though it is probably fine, it is about producing the evidence. They can't tell if the supplier is secure or not because they can't see in."
This lack of transparency suggests that cloud suppliers could have something to hide, said Rupert Brown, lead architect in the CTO office at UBS.
"If you can't see the architecture you are dealing with then there is probably something wrong," he said.
Meanwhile, Andrew Hatton, head of information systems at environmental organisation Greenpeace, believes that getting evidence of compliance from cloud suppliers was unnecessarily difficult.
"Even when you get the certificates [of compliance], it still feels very ad hoc. getting copies of those certificates is very hard work - harder than it should be," he said.
With green energy being a key concern for Greenpeace and one of the criteria it uses to choose suppliers, Hatton said that it was also tough to get energy data from cloud providers.
"Many [suppliers] do not want to answer the questions [on energy]," he said.
"The cloud is not green. It is often sold as green, but data centres are expanding, and that is really driving a big expansion in dirty energy."