BRUSSELS, July 29 (Reuters) - Norwegian browser maker

Opera filed a complaint about U.S. tech giant Microsoft ( MSFT )

to Brazilian antitrust authority CADE on Tuesday

alleging its Edge browser has an unfair advantage, underscoring

the long-running rivalry between the two companies.

Opera complained to the European Commission in December 2007

about Microsoft ( MSFT ) tying its Internet Explorer browser to

its Windows operating system. The case eventually ended with a

561 million-euro ($648 million) EU antitrust fine for the U.S.

company.

In July last year, Opera took the Commission to court for

exempting Edge from the Digital Markets Act, which aims to rein

in the power of Big Tech via a list of dos and don'ts.

In its complaint to CADE seen by Reuters, Opera alleged that

Microsoft's ( MSFT ) pre-installation of Edge as the default browser

across Windows devices and computers prevents rivals from

competing on the merits of the products.

"Microsoft ( MSFT ) thwarts browser competition on Windows at every

turn. First, browsers like Opera are locked out of important

preinstallation opportunities," Opera's general counsel, Aaron

McParlan, said in a statement.

"And then Microsoft ( MSFT ) frustrates users' ability to download

and use alternative browsers," he said.

Microsoft ( MSFT ) had no immediate comment.

Opera, which said it is the third-most popular PC browser in

Brazil, added that Microsoft's ( MSFT ) alleged tactics included giving

incentives to major PC manufacturers to pre-install Edge

exclusively on Windows on all their Windows devices.

Opera had 6.78% of the desktop browser market in Brazil in

June, according to StatCounter, versus Edge's 11.52% while

Google's Chrome held a commanding 75%.

Opera also alleged that Microsoft ( MSFT ) used anti-competitive

measures such as design tactics or dark patterns to steer PC

users away from rival browsers to Edge.

Opera called on CADE to investigate Microsoft ( MSFT ) and to demand

concessions to ensure fair competition.