The premier was reacting publicly for the first time since Abdurrahman Yalcinkaya, the court of appeals chief prosecutor, asked the constitutional court to ban the ruling party.
Yalcinkaya has accused the party of being opposed to Turkey's secular system.
Erdogan, speaking at a televised party rally in the southeast city of Siit, noted that 16.5 million people had voted for the AK in elections last July.
Erdogan said the party, which emerged in 2001 from a banned Islamist party, was fighting for democracy.
He also stressed the party's economic achievements since 2002.
On Friday, Hasim Kilic, the president of the constitutional court, announced that the prosecutor had called for the AK party to be shut down and 71 people, including Abdullah Gul, the Turkish president, to be banned from political activity for five years.
The court is due to meet on Monday to decide whether to accept the complaint.
The AK will have a month to prepare its preliminary defence after it is officially notified of a closure demand.
Turkey has a strictly secular ethos that underlies the constitution.
The constitutional court has previously banned several political parties, including the Welfare party of Necmettin Erbakan, Turkey's first Islamist prime minister and mentor of Recep Tayyip Erdogan, the current premier.
In recent months tensions have been running high between the secularist establishment, the powerful military, and the AK government.
Government critics have denounced a move to allow women to wear Islamic headscarves in universities, seeing this as a symptom of a slide towards religious rule.
The AK party, born of a coalition of Islamists, centre-right politicians and nationalists, denies having a secret Islamist agenda.