A prominent German politician has resigned from his party and from parliament in protest over coalition partner chancellor Angela Merkel's Greece politics.

Peter Gauweiler was deputy chief of the Christian Social Union, the Bavaria-based sister party of Merkel's Christian Democratic Union, and a well-known and critical follower of EU policies in the German Bundestag.

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He had been vocal about his opposition to the European Central Bank's (ECB) bond buying programme and euro-area bailouts.

In a statement published Tuesday (31 March), Gauweiler explained his dissatisfaction with the ruling coalition's reponse to Greek debt problems.

“I have publicly been requested - because I'm the CSU deputy - to vote in the Bundestag in such a way that is opposite to what I pleaded for at the Federal Constitutional Court and with my voters, and what I understand as the CSU programme”, he wrote.

“The Greek public debt … is not sustainable”, he wrote.

In February, Gauweiler was one of the German MPs that voted against Greece's bail-out extension. In his statement, he writes his opposition actually coincides with CSU policy.

“Why my dissenting vote against an extension of this programme should be a violation of CSU party discipline is beyond me.”

In his letter, the 65-year old politician also said the CSU promised there would be no eurobonds, but “the ECB has introduced de facto eurobonds with its new bond purchasing programme”.

Several hours after Gauweiler's resignation, Merkel held a press conference with visiting French president Francois Hollande, calling on Greece to quickly present its reform plans.

“There’s no time to lose”, said Merkel, adding “the quicker Greece makes proposals, the quicker an agreement can be reached”.

Greece's eurozone partners want to see a "credible" list of reforms by Athens before they give the go-ahead for bailout money to be released.

The on-going technical talks have a sense of urgency as Greece is expected to soon run out of money.

On Wednesday (1 April), officials from the eurozone's finance ministries will hold a teleconference to discuss progress.

EU Council president Donald Tusk said Tuesday that he hopes a deal between Greece and its creditors will be reached “by the end of April, for me it is possible”.

Meanwhile, Greek prime minister Alexis Tsipras shifted focus elsewhere on Tuesday by calling Western sanctions on Russia over its involvement in Ukraine a “road to nowhere”.

Greece could act “as a link and a bridge” to Russia, Tsipras noted.

The radical left PM is due to meet Russian president Vladimir Putin in Moscow on 8 April, amid speculation that he may ask Russia for financial aid.

While the visit will be closely watched, Merkel and Hollande on Tuesday both sought to play down its significance.

"We were also in Moscow and are nonetheless members of the European Union," said Merkel.