EU's longest-serving PM resigns, 'hopes' to return

"Are we responsible for something we did not know? I do not think so," he said.

He was accused by a parliamentary inquiry of having failed to control the Srel and to have "too often omitted to inform the parliamentary control committee or the judiciary of its irregularities, aberrations and illegalities."

"The intelligence service was not my top priority," Juncker admitted.

He added he hopes no Prime Minister of Luxembourg will consider the intelligence service a priority.

His opponents also criticised him for having spent too much time in Brussels as head of the Eurogroup of finance ministers, which held countless crisis-fighting meetings and prepared the bailouts of Greece, Portugal, Ireland and Spain in 2010-2012.

It is now up to the Grand Duke to dissolve parliament and call for early elections, which according to the finance ministry are likely to happen on 20 October. Juncker and his government will continue as caretakers until then.

Juncker, who is 58 years old, has not excluded the possibility of a comeback.

"I would like to run, but my party has to decide that," he said after meeting the Grand Duke.

The Christian Social People's Party has won every election since its creation, in 1944, except one election in the 1970s. On its webpage, the party posted Juncker's picture and the message: "Together with our Prime Minister."

Juncker has been a member of the Luxembourg government for over 30 years, first as finance minister and, for the past 18 years, as Prime Minister, making him the longest-serving premier in Europe.

He quit the Eurogroup job last year in order to focus more on domestic politics, after having held the office since its creation, in 2005.

Luxembourg's member of the EU commission, Viviane Reding, has been floated as a possible lead candidate of the Christian Democrats in the snap elections.

She has so far shown support for Juncker and said he is the "best [person] to govern our country."