The UK's Competition and Markets Authority (CMA) has defended its decision to block Microsoft's acquisition of Activision Blizzard.

As reported by Eurogamer, two of the organisation's execs – chair Marcus Bokkerink and CEO Sarah Cardell – appeared in front of members of Parliament to justify their move to block the deal.

"I understand the inference - that when a decision is made that blocks a deal, there are questions over whether the UK is open for business," Bokkerink said.

"All businesses know there's a very big difference between building a business, investing in a new business, investing in a startup, creating a new business - there's a big difference between that and buying an already-established, well-established firm with established positions. The two are not the same.

"The UK has always encouraged - and it is the CMA's duty to encourage - open competitive markets. We are vigilant - as it is our duty to be - to investments that consolidate an already-entrenched market power.

He continued: "I would challenge the premise that there is an impact on international confidence on doing business in the UK."

The UK is one of two jurisdictions in which the Microsoft Activision deal has been blocked. The other is the United States, where the FTC is suing to stop the merger.

The European Commission announced that it had approved the deal earlier this week.