A 52-year-old man first insulted the politician, Martin Schmidt, just after midnight and then attacked him with the ashtray, the police said on Friday morning.
Schmidt was taken to hospital but was discharged again on Friday morning, according to the AfD parliamentary group of the Mecklenburg-Vorpommern regional parliament.
According to the police, the attacker claimed to hold left-wing political views and to have acted out of political motives. The 52-year-old is now being investigated for dangerous bodily harm and insult.
AfD party chairman for Mecklenburg-Vorpommern Leif-Erik Holm said that this was a further escalation of political violence from the left.
"The attack is also the result of months of incitement and propaganda against our party," Holm added.
Nikolaus Kramer, regional parliamentary group leader of the AfD, spoke of a cowardly attack, saying: "Violence against politicians, regardless of party, is an attack on freedom of opinion and democratic discourse."