Ban also expressed concern about reported clashes between government troops and ethnic rebels since Sunday's vote "and urges all sides to refrain from any action that could raise tensions further or create instability at this sensitive time," his spokesman said in a statement.
The UN leader, who has frequently expressed frustration at the attitude of Burma's ruling generals, believes "the voting was held in conditions that were insufficiently inclusive, participatory and transparent," said the statement.
Sunday's vote has been condemned by much of the international community and Burma's opposition as a sham. Pro-junta parties are widely expected to take most seats in the new assembly and Aung San Suu Kyi, the Nobel Peace Prize winning opposition leaders was banned from taking part.
"Consistent with their commitments, the authorities must demonstrate that the ballot is part of a credible transition towards democratic government, national reconciliation and respect for human rights," said the UN chief's statement.
Ban "urges the Burmese authorities to release all remaining political prisoners and lift restrictions on Daw Aung San Suu Kyi without further delay so that they can freely participate in the political life of their country.
"He also urges the Burmese authorities to ensure that the process of forming new institutions of government is as broad-based and inclusive as possible."
Ban said: "The international community will look to the Myanmar authorities to provide greater assurances that the current process marks a genuine departure from the status quo."
The United Nations warned the junta before the election that it would not be seen as credible if Aung San Suu Kyi and other opponents remained in jail.
