Aung San Suu Kyi has been ordered to stop calling her home country Burma.
The official name was changed two decades ago to Myanmar by the previous regime, which said the term Burma was a legacy of British colonialism.
Ms Suu Kyi and her National League for Democracy party vigorously opposed the change.
The Election Commission ssued the statement after a recent visit to Thailand and Europe by Ms Suu Kyi, when she repeatedly referred to her country as Burma.
A statement published in The New Light of Myanmar newspaper said:
"As it is prescribed in the constitution that 'The state shall be known as The Republic of the Union of Myanmar', no one has the right to call (the country) Burma," it said in .
"Daw Aung San Suu Kyi called Myanmar 'Burma' in her speech to the World Economic Forum in Thailand on 1 June, 2012," the statement noted.
President Thein Sein has instituted a series of democratic reforms as the country emerges from decades of military rule.
The ABC reports this has seen many western nations ease sanctions against the country and members the current government.