The outgoing premier handed his resignation to King Albert II and hinted he might quit politics, saying it was time to do "other things". His coalition government suffered a devastating rejection in the wake of "Chickengate", the dioxin-in-chicken food safety scandal.
"I was not born in politics and I will certainly not die in it," said Mr Dehaene, a portly figure renowned for his abilities as a political fixer. "I always slept well, including last night, so don't worry about me, I will have no problem."
The main victors in Sundays elections were the Greens, who scored spectacular wins, and the Liberals who were outside the last government and not implicated in the dioxin scandal.
The Liberals - like all Belgian parties, split into Dutch and French- speaking camps - won 41 seats, a gain of two and the Green parties won 20 seats, an increase of nine. The Vlaams Blok, a far-right party of Flemish separatists, won four seats, going to 15 and tightening its grip in the north. But it failed in its attempt to paralyse the government of Brussels by winning seats from French-speaking parties.
The Flemish Liberal Democrats overtook Mr Dehaene's Christian Democrats as Belgium's strongest party, raising the prospect that the Liberal leader, Guy Verhofstadt, will be asked to form a new government. Mr Verhofstadt said he is ready "to take responsibility" and was due to meet the king last night.
But negotiations to form a coalition with a French speaking and Dutch majority could take weeks. Although an editorial in the Belgian daily Le Soir declared Mr Dehaene's party as in a "coma" and called the vote a cry for change, the outcome may only increase the fearsome complexity of the deal-making required to build a Belgian government.
Christian Democrats and socialists who took part in the last coalition could even return as junior partners. How the new administration will handle the surge in support for the Greens remains another imponderable.
Mr Dehaene was the great survivor of Belgian politics, having stayed in office despite the bungled inquiry into the case of Marc Dutroux, the man accused of several child murders, and his later escape.
But the dioxin scandal proved one crisis too many. "The economic damage will be very big," Mr Dehaene told journalists on Monday. Last week, Belgium gave a rough economic damage estimate of close to $1bn.
The health scare emptied supermarket shelves of meats and dairy products, set off worldwide bans on Belgian products and a trade dispute between Europe and the US.
Mr Dehaene said a new government was needed urgently to cope with the fallout of the scare. He said: "This [affair] is of such magnitude that I don't see with what authority a caretaker government could take important initiatives. So we need a fully fledged government that can tackle this problem quickly."Reuse content