In a manifesto published on Saturday, senior conservatives including former EU agriculture commissioner Franz Fischler and ex-vice chancellor Wilhelm Molterer, both from the People's Party (ÖVP), said the next president must be "dependable".
To protect its economic vitality, "Austria must remain a trustworthy European and international partner," they wrote.
The manifesto offered support for Hofer's liberal rival, the independent ecologist Alexander Van der Bellen.
Hofer, who heads the far-right Freedom Party (FPÖ), has not ruled out a referendum on Austria's future in the European Union following Britain's shock vote in June to quit the EU.
"We do not want to be faced with speculation about Austria leaving the European Union nor with attempts to hide the cornflower behind a crucifix," the declaration said, referring to a recent controversy.
The 45-year-old has been accused by Christian groups of manipulation after he added the phrase "So help me God" to his campaign posters.
Election poster for Hofer showing "So help me God." Photo: Paul Gillingwater
He has also been criticised for wearing a cornflower, a blue flower with a controversial past which was used by banned Austrian Nazis in the 1930s to identity each other. Hofer has insisted he only wore it for the blue -- the colour of the FPÖ.
Like populist parties elsewhere in Europe, the FPÖ is currently leading national polls.
Hofer, hoping to become the EU's first far-right head of state in the December 4 poll, has been stoking public fears about record immigration and rising unemployment.
Austria's president must be a guarantor of co-existence and "that is incompatible with speeches about fear, hate and the constant search for scapegoats," the manifesto said.
The ÖVP has not given its followers official voting recommendations but many of its senior members have already said they would back Van der Bellen.
The independent ecologist ran against Hofer in May, winning by a narrow margin although the result was later dramatically overturned by Austria's highest court which upheld claims of procedural irregularities brought by the narrowly-defeated far-right.
Opinon polls suggest the outcome of the re-run is too close to call.