Poland's Prime Minister Kazimierz Marcinkiewicz has tendered his resignation following reports of a growing rift with his party's chairman.
He took up the position last October following his party's election victory
It was not clear when his resignation would take effect, a statement from the Law and Justice party (PiS) said.
The party has recommended the post be taken over by its chairman Jaroslaw Kaczynski - the identical twin brother of President Lech Kaczynski.
It was not immediately clear if he would take up the vacancy.
"Prime Minister Kazimierz Marcinkiewicz has told the PiS authorities that he plans to resign," the statement said, without giving any reason for his decision.
"The PiS political committee has unanimously recommended Jaroslaw Kaczynski for the post of prime minister," it added.
Over recent weeks, there had been frequent reports of a rift between Mr Marcinkiewicz and Jaroslaw Kaczynski over economic policy.
When the Law and Justice party won last October's parliamentary elections, Mr Kaczynski appeared to be the front runner to take on the role of prime minister, but he turned down the job.
At the time, his brother was due to participate in the second round of the presidential elections and Mr Kaczynski said it would be wrong for both brothers to hold the two top posts.
If Jaroslaw Kaczynski does take up the new vacancy, the Kaczynski brothers would be the world's only twins to hold the two highest posts in any country.
A former physics teacher, Mr Marcinkiewicz was previously the party's economic adviser head of the parliamentary treasury commission.