Cloud computing competition is being stifled by so-called “hyperscalers” like Amazon Web Services and Microsoft Azure.

According to Ofcom, 60% to 70% of cloud spending goes to AWS and Azure.

Microsoft and Amazon dominate the cloud computing market, according to Britain’s anti-competition regulators.

The Competition and Markets Authority has been referred Ofcom’s inquiry for further investigation.

Ofcom said that it has identified features that make it harder for organizations to switch cloud providers, or to use multiple cloud services, and that Amazon and Microsoft are particularly vulnerable.

There is no clear evidence that competition is working well, Fergal Farragher, Ofcom’s director responsible for the market study, said in a statement.

To ensure business customers continue to benefit from cloud services, we’re referring the market to the CMA.”

Amazon Web Services and Microsoft Azure are limiting competition in the cloud computing market, Ofcom says. Companies like these enable businesses of all stripes to do critical computing tasks over the internet, as opposed to using on-site servers or “on premise” servers.

In a statement on Thursday, Amazon said it disagreed with Ofcom’s findings. A Microsoft spokesperson was not immediately available for comment.

Market leaders are Amazon Web Services and Microsoft Azure. In contrast, Microsoft prioritizes big enterprises with its cloud solution. According to Ofcom, AWS and Azure account for 60% to 70% of cloud spending. Ofcom estimates the cloud infrastructure services market in the U.K. is worth £15 billion ($18.2 billion), generating roughly 81% of revenue.