One of three Turkish cabinet ministers who have resigned over a corruption scandal, Environment Minister Erdogan Bayraktar, has urged Prime Minister Recep Tayyip Erdogan to step down.
Mr Bayraktar, Economy Minister Zafer Caglayan and Interior Minister Muammer Guler quit after their sons were taken into custody.
All three deny any wrongdoing.
Police are investigating allegations of illicit money transfers to Iran and bribery for construction projects.
All three ministers had appeared with Mr Erdogan in front of a crowd of supporters on Tuesday night on his return to Esenboga airport in Ankara from a trip to Pakistan.
In a telephone interview with NTV television, Mr Bayraktar complained of being put under pressure to resign by Mr Erdogan.
He insisted that "a great proportion" of construction projects that were under investigation were approved by the prime minister himself, adding: "I want to express my belief that the esteemed prime minister should also resign."
In a further blow to Mr Erdogan, MP and former interior minister Idris Naim Sahin said he was resigning from the ruling AK Party.
Mr Erdogan was reportedly meeting the president late on Wednesday with details of his new cabinet.
'Cash in shoe boxes'
The sons of Mr Caglayan and Mr Guler, along with the chief executive officer of the state-run bank Halkbank, are among 24 people who have been arrested on bribery charges.
Mr Bayraktar's son was detained as part of the inquiry but later released from custody.
Media reports say police seized $4.5m (£2.75m; 3.29m euros) in cash that was stashed in shoe boxes in the home of the bank's CEO, while more than $1m in cash was reportedly discovered in the home of Mr Guler's son, Baris.
Mr Erdogan has denounced the corruption probe as a plot by foreign and Turkish forces to discredit his government ahead of local elections in March.
But he said his ruling party would not try to sweep the allegations under the carpet.
"The AK Party does not overlook or tolerate corruption. If it does, it will have removed its raison d'etre," Mr Erdogan told a meeting of his party in the capital, Ankara.
Commentators believe the scandal stems from a power struggle between Mr Erdogan's government and an influential US-based Muslim cleric, Fethullah Gulen, who is said to have many followers within Turkey's police and judiciary.
Mr Gulen, who has denied any involvement in the investigation, left Turkey in 1999 after being accused by the then government of plotting to establish an Islamic state. He was cleared of that charge but has never returned to Turkey and now lives in Pennsylvania.
The government has dismissed dozens of police officials who were either involved in the investigation or thought to be linked to Mr Gulen.
Journalists have been prevented from entering police buildings, leading to claims that the government is trying to impede the investigation.
The opposition had long called for Mr Caglayan and Mr Guler to resign, saying they should not remain in positions where they would be able to influence the investigation.
As he resigned on Wednesday, Mr Caglayan questioned the legitimacy of the investigation.
"It is clear that the operation is a dirty conspiracy against our government, our party and our country,'' he said in a statement.
"I am leaving my position at the economy ministry to spoil this ugly plot, which has involved my colleagues and my son, and to allow for the truth to be exposed.''
Mr Guler told reporters on Tuesday that he was the victim of a political plot and that there is nothing his family could not account for.
He also said alleged wiretap recordings of a conversation with his son - reportedly used as evidence by police for the arrests - were tampered with, and that the cash discovered in his son's house was money earned from the sale of a villa.