"I wish her all the best but it would be better for her to step down because of her failure in the migrant policy," Willy Wimmer, who also served as a state secretary in the German Defense Ministry, said.
Merkel was named Person of the Year by US Time magazine on Wednesday for "asking more of her country than most politicians would dare" in the face of a rising influx of migrants into Germany.
Wimmer said it was "dangerous" to be featured on the cover of a US magazine. Time bestows the title every December to the person or persons it considers had the greatest impact – for better or for worse — on the world that year.
Germany has been grappling with a severe migrant crisis that hit Europe earlier this year. Bavaria's Social Minister Emilia Mueller said on Wednesday that, since the beginning of 2015, the number of asylum applications registered in Germany had surpassed one million.