German Chancellor Angela Merkel said she will consider changes in the law to make it easier to deport migrants who commit crimes.
It comes as more than 120 complaints of theft, sexual assault, and two alleged rapes on New Year's Eve in Cologne are being investigated, sparking a debate about Germany's open-door policy on migrants.
The police's handling of events has been sharply criticised with the head of the city police force suspended from his duties.
Victims described chaos as dozens of sexual assaults and robberies were carried out with little apparent response from the authorities.
The party leadership is holding a policy meeting on the issue in the city of Mainz today.