Myanmar on Friday "resolutely" rejected a ruling by the International Criminal Court empowering the tribunal to probe alleged crimes against the Rohingya even though the Southeast Asian nation is not a member of it.
Around 700,000 of the stateless Rohingya Muslim minority were driven into Bangladesh by a Myanmar army-led crackdown last August.
They have given detailed and consistent accounts of a relentless campaign of murder, rape and arson that forced them to flee.
Myanmar denies any systematic abuses, insisting its military actions were a proportionate response to attacks by Rohingya militants.
In an unprecedented ruling on Thursday the ICC said it had jurisdiction over the crisis because of the cross-border nature of the alleged "deportations" of the Rohingya to Bangladesh. But in a stinging response late Friday from a government besieged by criticism, Myanmar said the decision was "of dubious legal merit".
"The decision was the result of manifest bad faith, procedural irregularities and general lack of transparency," a statement released by the president's office said, adding the country "resolutely rejects" the court ruling.
Myanmar was "under no obligation" to respect the ICC decision, it said, adding allegations of deportation "could not be further from the truth".
Myanmar, which denies the Rohingya citizenship and has for years subjected them to apartheid-like conditions inside its western Rakhine state, says it is ready and willing to take those who fled back.
But a "repatriation" deal with Bangladesh has so far not resulted in any serious numbers of returns.
Refugees in the overcrowded, fetid Bangladeshi camps say they will not return to Myanmar without citizenship and the accompanying rights, as well as security guarantees and compensation for seized land and razed villages.
The ICC ruling on Thursday significantly ups the ante on Myanmar, allowing the ICC's chief prosecutor to open a preliminary investigation that could lead to a wider probe and eventually a trial.