The accusations were the latest salvo in a row that is likely to be one of many during a period of cohabitation, where the government and head of state are from different political camps.

Prime Minister Donald Tusk said both Duda and nationalist Law and Justice (PiS) party leader Kaczynski could be held responsible for obstructing justice.

"The situation is unbelievable. Convicts ... are to be taken to a place of solitary confinement, but they choose another, more comfortable place of solitary confinement - the presidential palace," Tusk said.

In 2015, weeks after the PiS came to power, Duda issued a pardon to Mariusz Kaminski after he was convicted of abuse of power in a previous role, allowing him to become interior minister.

Lawyers questioned whether Duda could pardon him before an appeals court issued a final ruling. The Supreme Court said last year the case should be reopened and in December Kaminski and his deputy Maciej Wasik were sentenced to two years in prison for abuse of power.

On Tuesday, the president's office posted a picture of Kaminski and Wasik with Duda at an official event at the palace.

"A sombre dictatorship is being formed. We cannot allow for Poland to hold political prisoners," Kaminski said after the event, before reentering the building.

"We are dealing with a deep crisis of our state, a rebellion in the courts ... we are not hiding, we are at the president's."

According to Szymon Holownia, the speaker of the lower house of parliament, or Sejm, the December verdict meant Kaminski and Wasik lost their parliamentary mandates. But both have denied that and plan to attend the next sitting.

Duda met Holownia on Monday to try to convince him his pardon was valid and the court had no right to issue a second verdict, but they did not come to an agreement.

"The sitting planned this week will be moved to next week... there is one reason for this decision - my task is to ensure the dignity of the Sejm and social calm," speaker Holownia said.

The parliament had been due to vote on the 2024 budget at this week's sitting. It has until the end of January to send it to the president for him to sign. If it does not do this the president can dissolve parliament.

(Reporting by Anna Wlodarczak-Semczuk and Pawel Florkiewicz; Editing by Alan Charlish and Christina Fincher)