Laurette Onkelinx, a Socialist MP, spoke amid angry recriminations after King Albert II appointed two new negotiators to form a government straddling Dutch and French-speaking fractions.
Elio Di Rupo, the Socialist leader gave up efforts to seal a coalition pact with the biggest Flemish party, the independence-minded N-VA, seven weeks after a general election returned a deadlocked parliament.
"Let's hope it doesn't come to that because if we split, it will be the weakest who will pay the heaviest price. On the other hand, we can no longer ignore that among a large part of the Flemish population, it's their wish," Miss Onkelinx told La Deniere Heure newspaper. "So yes, we have to get ready for the break-up of Belgium.
"When I look at the letters I receive, loads of people think it's possible."
Meanwhile, Herman Van Rompuy, President of the European Council and a former Belgian PM said he still believed there was a chance of a breakthrough in the tortuous negotiations.
He said: "In all difficult periods there is a moment when you have to put the details to one side and not keep on discussing until the last million or the last comma.
"You have to say we're taking a risk and making a leap forward in the process of state reforms and a settlement. We have to stand up to our followers, on both sides, Flemings and Francophones, and move forward. It's the only way to reach a solution."
