Google's rivals have strongly criticised the search engine's newest proposals to settle its long-running antitrust case with the European commission. The internet company has also been accused of slowing down the arbitration process, which has so far ground on for three years and might not be resolved before next spring.

Documents outlining Google's proposals to tweak its presentation of search results are currently being considered by 125 organisations across Europe.

The latest proposals are supposed be confidential. However, the Guardian has seen two separate copies of the proposals, through which Google is trying to avoid a full-on legal battle with Joaquín Almunia, the commission's antitrust chief. At least one copy has also been leaked to the Financial Times.

Almunia's office announced in November 2010 that it was investigating Google over potential abuse of its monopoly position on internet search in the European Union, where it has over 90% of search traffic. In May 2012 Almunia said that a key commission concern was that "in its general search results, Google displays links to its own vertical search services differently than it does for links to competitors".

Under the leaked proposals, Google would continue to show links to its own sites – such as maps, YouTube and shopping – prominently in search results, and give rivals only limited exposure. On desktop searches, rival sites would be shown as small links below Google's own larger "sponsored" links, with an option for the user to hide them. On mobile phones, there would be a link to "other sites" beside Google's sponsored links at the top of searches. Users would have to click the link to see the rival offerings.

The new proposals were dismissed by rivals, who also rejected an earlier set of public proposals in April, on the basis that Google could still use its monopoly in search to corner the separate markets of paid shopping and maps searches.

Shivaun Raff of Foundem, the British search company, was one of the first to complain to the commission about what she says was Google's manipulation of search results to reduce her site's visibility. She looked at the new documents and told the Guardian: "Google's revised proposals remain fundamentally unchanged and suffer from all of the same fatal flaws that rendered its previous proposals considerably more harmful than helpful.

"Were the commission to adopt anything along the lines of these proposals it would be aiding and abetting Google in its long-running strategy to transition organic traffic into paid traffic. As with Google's previous proposals, it would be better for the commission to do nothing than to adopt them."

The proposals were sent out last week to 125 interested parties for comment. At the time Google's spokesman in Brussels, Al Verney, said: "We've made significant changes to address the commissions's concerns, greatly increasing the visibility of rival services and addressing other specific issues." He added: "Unfortunately, our competitors seem less interested in resolving things than in entangling us in a never-ending dispute."

But David Wood, chief lawyer for the lobbying group Icomp, part-funded by Microsoft, fired off an angry response to Verney: "If speed and a genuine resolution is really a concern for Google, then why not publish both your [revised] proposal and data that supports it for all to be able to comment on?" he said, adding that it was "undeniable" that Google had slowed down the resolution process.

Since spring 2011 the two sides have been negotiating as Google tries to avoid a statement of objections, which could lead to a fine and court-imposed sanctions on how it presents its results. Almunia, meanwhile, is seeking a negotiated settlement that also satisfies rivals' complaints.

The 125 organisations have until 28 November to respond to the proposals.

Raff added: "It is difficult to imagine a competition case where the stakes for consumers, businesses, and innovation could be any higher.

"Google's overwhelming dominance of search means that it plays a decisive role in determining what the vast majority of us discover, read, use, and purchase online. The importance of ending Google's ability to manipulate this unprecedented market power to its own anti-competitive ends cannot be overstated."