And it has insisted no rules were broken in hiring the Eurocrat while offering a complex explanation as to why Mr Selmayr was slotted into his new post on the same day predecessor Alexander Italianer confirmed he was to retire.
Meanwhile, it has emerged that Mr Selmayr had a rival for the post of secretary-general – lawyer Marinez Alberola, who subsequently withdrew her application – and was later given Mr Selmayr’s old job.
The Commission had been pressed for answers by the European Parliament’s Budget Control Committee and MEPs concerned at the circumstances in which Mr Selmayr landed his new job.
Mr Juncker’s Commission was given a 3pm deadline on Saturday to submit answers.
European Commission President Jean-Claude Juncker confirmed Mr Selmayr in his new role on February 21, and has steadfastly backed him ever since, even threatening to resign if the German lawyer is forced out.
MEPs including Green Party representative Sven Giegold had submitted a lengthy list of questions about the appointment, and were expecting answers by yesterday.
However, the detailed response only arrived in the early hours of Sunday morning.
A press release issued by the Commission stated: “The option for Mr Selmayr to become Secretary-General only became concrete for him on 20 February 2018 – after his interview with Commissioner Oettinger and after the President had consulted Commissioner Oettinger and First Vice-President Timmermans.
“President Juncker explained during his press conference on 21 February that when agreeing to become Secretary-General in 2015, Mr Italianer had told the President that he intended to retire soon after 1 March 2018.
“The President discussed this information with his Head of Cabinet, like he does with all important senior management matters.
“The President did not share this information further in order not to undermine Mr Italianer’s authority while he was in office.
“The President and his Head of Cabinet also kept the hope to be able to convince Mr Italianer to stay on as Secretary-General beyond 1 March 2018.
“However, in early 2018, Mr Italianer confirmed that he would stick to his decision.
Mr Italianer sent the President a formal letter stating his intention to retire on 31 March 2018 on the morning of 21 February 2018. After having sent this letter in the morning, he subsequently informed the College of Commissioners during their meeting on 21 February.”
A spokesman added: “Today, the European Commission replied to the 134 questions by the Budgetary Control Committee of the European Parliament on the Appointment of Mr Selmayr as the new Secretary-General of the European Commission which it had received on Tuesday (20 February 2018).
“In its replies the Commission confirms that the decision to appoint Mr Selmayr was taken in full compliance with the EU Staff Regulations and the Rules of Procedure of the Commission.
The document sent to MEPS also confirmed that Ms Alberola had applied for the post of secretary-general as well as Mr Selmayr on February, only to withdraw her application later.
Ms Arberola was confirmed as Mr Juncker’s head of cabinet (the post previously occupied by Mr Selmayr) on February 20 – the day before the press conference at which Mr Juncker announced Mr Selmayr’s appointment.
Mr Giegold said: “Selmayr investigation: Today at 3 at the @ EU_Commission has sent an 80 page document with its answers to the 130 questions by the European Parliament on # SelmayrGate. Best weekend read ever!”