Turkey on Friday accused Germany of working for a "No" vote ahead of an April referendum on whether to boost President Recep Tayyip Erdogan's powers in an executive presidency.
"They don't want Turkey to campaign here, they are working for a 'No'. They want to get in the way of a strong Turkey," Foreign Minister Mevlut Cavusoglu told reporters in Ankara after German local authorities blocked rallies where Turkish ministers were due to speak.
The Turkish public will vote on April 16 on whether to create a system which Ankara says will be like that of France and the United States and ensure political stability.
However, critics say the system will weaken parliament further and lead to one-man rule.
Tensions have increased in recent days between Turkey and Berlin after Ankara's provisional detention of a German journalist on terrorism-related charges on Monday.
Justice Minister Bekir Bozdag scrapped his visit to address the Turkish community in the western German town of Gaggenau on Thursday after local authorities withdrew an agreement to allow the rally.
He had also been due to meet his German counterpart.
Cologne city authorities meanwhile said they would no longer allow the Union of European Turkish Democrats (UETD) to use a hall on Sunday, when Turkish Economy Minister Nihat Zeybekci was expected to make a speech.
The row deepened after the Turkish government summoned Germany's ambassador to Ankara on Thursday in protest at the cancellation of the rallies.
Cavusoglu hit back at the moves by German officials, accusing them of double standards and failing to "honour democracy, freedom of expression or freedom of assembly".
Ahead of an election later this year, Cavusoglu warned Germany to "stay far away from populism" and told Germany it would "need to learn how to behave towards Turkey" if Berlin wanted to maintain relations.
"You must see us as an equal partner," he added.