Britain's Competition and Markets Authority (CMA) launched an investigation into the country's cloud computing industry in October, following a referral from media regulator Ofcom that highlighted Amazon and Microsoft's market dominance.

In a letter published on the CMA's website on Tuesday, Amazon said changes to Microsoft's terms of service had made it difficult for customers to switch to alternative cloud providers or run competitors' services alongside. "To use many of Microsoft's software products with these other cloud services providers, a customer must purchase a separate license even if they already own the software," Amazon said.

"This often makes it financially unviable for a customer to choose a provider other than Microsoft."