It also calls for the order of the five ballot screens to be scrambled, instead of the browsers being listed alphabetically from left to right.
The order of browsers on the screen is a big issue for Mozilla, which could find itself in the least desirable right side of the screen if the list remains in alphabetical order by company name.
"If these warts are not removed it would be sad for the Web and sad for competition," Wium Lie said in a telephone interview, adding that the Commission has "a unique once-in-a-lifetime opportunity" to correct the imbalance in the browser market.
ECIS is expected to take a tougher line in its response, due in with the antitrust officials by Monday.
"Experience in the E.U. and the U.S. has unfortunately demonstrated that anything less than a robust settlement agreement accompanied by effective compliance verification measures will likely lead to inadequate changes in Microsoft's behavior and a failure to redress damage resulting from many years of abusive practices," one person close to ECIS said, reading from a draft of the group's formal reply to the Commission.
French consumer group UFC Que Choisir is broadly in line with Opera and the other companies in its concerns about Microsoft's offer. Like them UFC Que Choisir is recognized as an interested third party in the antitrust case.
"Dramatic changes are needed," said Edouard Barreiro, an expert following the IT industry for UFC Que Choisir.
"We support the ballot screen but Microsoft's idea for it will bring nothing in the form it is in now. We want the Commission to press Microsoft to make significant changes," he said, mentioning the same issues raised by Opera and others.
ECIS, Google, Mozilla and the Commission were also unavailable to comment.
Microsoft had a prepared statement that didn't address the specific concerns of the groups. The statement concluded: "We look forward to the next steps in the process."