LONDON The head of Britain's anti-trust regulator said it was not seeking to create a "hostile environment" for tech companies with its decision to block Microsoft's $69 billion acquisition of Activision Blizzard.

The Competition and Markets Authority (CMA), which operates independently from government, caused shockwaves in April when it said the deal could not go ahead because it would hit competition in the nascent cloud gaming market, drawing a rebuke from Microsoft.

Its president Brad Smith has accused the regulator of undermining confidence in Britain as a destination for tech businesses, worrying lawmakers who are pinning their hopes on Britain's science and innovation sector to help drive growth.

CMA Chief Executive Sarah Cardell told a panel of lawmakers on Tuesday that she stood by the decision, even after Brussels gave its approval on Monday.

"This is a sector where we want to make sure together that we can create and support the best conditions for competition that will enable companies big and small to thrive, including many UK startups, many UK competitors," she said.

Cardell added that the CMA had engaged widely with companies across the sector. "I don't find that we are operating sort of, broadly speaking, in a hostile environment," she added.

Microsoft has said it will appeal the ruling.

The U.S. Federal Trade Commission has also filed a complaint to block the deal, which Microsoft has indicated it will fight.

(Reporting by Sarah Young and Paul Sandle; Editing by Kate Holton)