The announcement has come following the Public Ministry revealed that it is the target of an independent investigation by the Supreme Court of Justice into lithium and hydrogen projects.

In a communication to the country, from his official residence, in S. Bento, Lisbon, the prime minister justified his decision by stating that “the functions of prime minister are not compatible with the suspicion of any criminal act”.

"Obviously, I submitted my resignation to the President of the Republic," he said.

The communication to António Costa's country, from the prime minister's official residence, also follows searches in São Bento, targeting his chief of staff, Vítor Escária, and members of his Government.

António Costa submitted his resignation after almost eight years in office as Prime Minister, a position for which he was sworn in on November 26, 2015, by the then-President of the Republic, Aníbal Cavaco Silva.