The third opposition party at the Turkish Grand National Assembly, the People's Democratic Party (HDP), is opposing the constitutional changes along with Turkey's main opposition party, the Republican People's Party (CHP).
The HDP leadership is staunchly secularist and draws at least some ideological inspiration from Abdullah Ocalan, who founded the PKK as a Marxist-Leninist armed organisation in 1974.
The PKK is considered as a terrorist organisation in the eyes of Turkey, the US and the EU.
HDP argue that the referendum is taking place in an unfair environment for opposition parties.
Here are HDP arguments against proposed constitutional changes:
• They argue that the constitutional amendments will result in one-man rule.
• The HDP announced that they are going to campaign for ‘no' in the referendum and, they plan to campaign separately from CHP because, CHP's intention is to maintain the status quo while they demand a "democratic, civilian and pluralist constitution."
• They also claim that making constitutional changes while a number of HDP MPs are detained, means ignoring a part of society.