Fighting the causes of the refugee crisis has come to sound like “a hollow phrase”, Cem Özdemir, Green Party leader, told the Funk Media Group.
Hundreds of thousands of Syrians are trapped in Aleppo in northern Syria, said Özdemir.
“This is an unimaginable misery - and the world barely takes any notice. Angela Merkel is completely ignoring this and other humanitarian catastrophes.”
He was ashamed, he said, “due to the failure of the world community, of Europe and above all of Germany".
At her summer press conference on Thursday, Merkel pledged to do more to fight the causes of the refugee crisis which has brought hundreds of thousands of asylum seekers to Germany over the last 12 months.
During her speech, Merkel reaffirmed her pledge that “we'll manage this” while also saying that three refugees who had committed bloody crimes in Germany in previous days had “mocked the country".
Dietmar Bartsch, co-leader of Die Linke (the left Party) also criticized the Chancellor, saying that fighting the causes of the refugee crisis means bringing peace to conflict zones and supporting economic development.
Merkel has also faced criticism from the right since her speech.
Frauke Petry, leader of the Alternative for Germany (AfD) told her to “stop repeating ‘we'll manage it' and finally admit your mistake.”
The AfD strongly rejects Germany's decision to open its borders to refugees.
In March, Germany appeared to reverse its generous policy towards asylum when it pushed through an EU deal with Turkey on refugees.
Under the scheme, one Syrian refugee is settled in Europe legally in return for every migrant taken back by Turkey from EU member Greece.
Since that agreement was reached, refugee arrivals in Germany have dropped dramatically.
Aid groups have criticized the agreement, warning that the Greek registration sites would become de facto detention centres for people slated to be sent back to Turkey after risking their lives and spending a small fortune just to reach Europe.