Liberty Global, set up by U.S. cable pioneer John Malone, said on Monday it has offered to buy up to 500 million Swiss francs in newly created Sunrise shares to help finance the purchase.
But Freenet, which holds nearly a quarter of the stock in Sunrise, said it still opposed the deal which it said is too expensive.
Investors are due to vote on Oct. 23 on a 2.8 billion franc capital hike to help fund the purchase.
"The participation of Liberty Global changes nothing in our opinion or that of the majority of shareholders about the deal," Freenet said.
"We still think that it is not a good deal," it said. "Liberty Global has merely said it will participate at rock bottom prices with the money they will receive from a too expensive sale."
(Reporting by John Revill and Oliver Hirt; editing by Jason Neely)