Jean-Claude Juncker - who chaired eurozone meetings for some 10 years and who, until last year, was the EU's longest-serving prime minister - has again said he is keen to be the next European Commission chief.

"I would be in principle willing to run, if the programme and other things are right," the 59-year old Luxembourg politician told German RBB radio on Thursday (9 January).

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As the potential candidate of the European centre-right, he added that he relishes the idea of a "lively" debate with Martin Schulz, the offficial centre-left candiate and current European Parliament head.

Juncker's nomination remains uncertain, however.

EU centre-right leaders have said they will decide on the name at a European People's Party congress in March in Dublin.

Key to the process is the only woman among the EPP leaders - German Chancellor Angela Merkel - who, according to Der Spiegel magazine, is not so keen on Juncker's return to the European scene because he often criticised Germany's handing of the economic crisis.

Merkel's spokesman has rejected the Spiegel report.

Juncker himself underlined his "friendly" relationship with the German leader, saying he telephoned her twice in the past three weeks.

The current Luxembourg Prime Minister, Xavier Bettel, also spoke with Merkel on the phone. "She reassured me that she does not plan to deprive Europe of the former Eurogroup chief's competences," Bettel told L'essentiel newspaper on Wednesday.

But for his part, Jeroen Dijsselbloem, the Dutch finance minister who took over from Juncker as Eurogroup chair, is not helping Juncker's campaign.

Dijsselbloem told a late-night talk show on Dutch TV on Monday that Juncker is a "heavy smoker and drinker."

He added that since Juncker left the post, the atmosphere during finance ministers' meetings "has become much more Calvinistic."

Rumours on Juncker's bad habits have been doing the rounds in Brussels for years. But Dijsselbloem is the first ever to break the taboo on the subject.

His remarks prompted Juncker to retort on Wednesday, according to Luxembourg Wort, that "I don't have a drinking problem ... and I don't want to react to comments made in a humoristic talkshow on Dutch television."

Meanwhile, Michel Barnier, the French EU commissioner in charge of financial services and the internal market, still believes he might get the centre-right nomination, writes Le Monde.

A book written by the French politician is currently on standby depending on whether the text can describe him as a "candidate" for the EU commission presidency or not.

Barnier may be a member of the cntre-right "EPP" group, but the current French government is not, meaning he lacks a top-level advocate for his bid.

The Rheinische Post has also floated the name of another French politician - Christine Lagarde - for the commission top post.

The nomination process is this time around taking place in a new atmosphere.

Under the Lisbon Treaty the political faction which does best in EU elections in May is to get preference in the top jobs race.

But Merkel last year ruled out any automaticity in the process.

Her position means the final appointments are likely to be settled as in the past - in behind-the-scenes bargaining on a package of powerful posts, including the head of the EU council, the EU foreign affairs chief, the Nato head and the European Parliament chairman.

Aside from political affiliation, the bargain traditionally involves considerations on countries representing the north, south, east and west, as well as the need to have at least one woman in the top phalanx.