Fawzi Barhoum was quoted as saying the visit by Ziad al-Bandak, adviser to Palestinian President Mahmoud Abbas, was "unjustified and unhelpful".
He also called the Holocaust an "alleged tragedy", media reports say.
Hamas spokesmen have previously described the Holocaust as fabricated.
More than a million people, mainly Jews, were murdered at Auschwitz, part of some six million Jews killed in the Nazi genocide during World War II.
Mr Bandak visited the camp late last month and paid his respects there to the dead.
Mr Barhoum is quoted in media reports as saying the visit is at "the expense of the true Palestinian tragedy".
A comment piece published by the Hamas-run Filastin newspaper also criticised Mr Bandak's visit.
"What is the wisdom in such a simple step that supports the Jews and their crimes?... Neither the Jews nor we believe that Hitler killed six millions Jews," the article read.
In 2009 the Hamas-led administration in the Gaza Strip resisted attempts to introduce lessons about the Holocaust in UN-run schools.
A spokesman for the Palestinian militant movement Hamas has criticised a visit by a Palestinian official to the Nazi death camp at Auschwitz, media reports say.