Turkey's main opposition party on Saturday said state television had banned its campaign advertisement for June 7 legislative elections.
The Republican People's Party (CHP) said it had been informed by state broadcaster TRT that it would not show the advertisement on the grounds it directly targeted the ruling Justice and Development Party (AKP).
Turkey's opposition has long accused TRT of showing high levels of bias towards President Recep Tayyip Erdogan and the AKP, which he co-founded.
"By taking the decision not the broadcast the advertisement, TRT has created a new scandal," the CHP's deputy leader Bulent Tezcan said in a statement on the party's website.
"The main purpose of state-funded television in all democratic countries is fairness of broadcasting.
"TRT's direction are committing the crime of abuse of public office," he said, vowing to start legal proceedings.
The advertisement, with the slogan "We applaud as a nation" and set to gritty percussion music, urged voters to attend the CHP's first mass election rally this Saturday.
"How can you carry out politics in a democracy when the opposition cannot target the government? I'm open to suggestions," said senior CHP official Enis Berberoglu, quoted by Turkish media.
The controversy comes after an Ankara court Thursday ordered the CHP's leader Kemal Kilicdaroglu to pay damages after ruling that he insulted Erdogan in a speech in 2013.
The AKP has long stood accused by critics of monopolising air time on state and pro-government private television channels.
Analysts are expecting the election campaign to be a fierce battle.
While the AKP is widely expected to win, it has its work cut out to realise its target of winning a constitutional majority needed to change the basic law to create a presidential system in Turkey.
Kilicdaroglu on Saturday kicked off the CHP's election campaign with a mass rally attended by thousands in the Kartal district on the Asian side of Istanbul.
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