"Mr. Erdogan and his government are not welcome in our country… If he comes he should not be allowed, in my opinion, to make an appearance. This would threaten our country’s security," Volker Bouffier told the Deutschlandfunk radio.
The war of words between Turkey and Germany escalated over the weekend when Erdogan accused Merkel of taking "Nazi measures" against his ministers and 1.4 million of eligible ethnic Turkish voters.
Germany came under a barrage of Nazi-themed jibes from Erdogan, who hit the campaign trail last month to drum up support for a reform that will give him greater executive powers. Bouffier ruled out Erdogan would tone down his rhetoric after the mid-April vote on it.