"But as the good sense is unequally spread, I believe that this idea has no chance of being accepted," the prime minister of Luxembourg said in a scathing attack on the EU leaders' rigidity during talks concerning the European constitution.
Juncker warned that if small member states refuse to accept this "reduced Commission", the large states would reinstate their demand for a European Council president "with absolute powers".
"And then what small states perceive as a big victory would be a huge blow for the efficiency of the [EU] system." Speaking exclusively to European Voice, he criticized "this new fashion in Europe of everybody explaining 'the red lines' even before negotiations start.
"It will trigger failure," he warned. The red lines, an expression used by EU leaders in their talks on the constitution, designate taboo areas, such as defence or taxation, that some governments want to keep out of the Union's reach. But Juncker warns this "risks engulfing the IGC [intergovernmental conference] in a scenario that allows no progress".
"I believe many government leaders like saying some things in the negotiation room just to be able to repeat them outside, in the press room. But we run the risk of becoming rigid. By repeating all over again our national positions we become incapable of compromising. Our method is no good."
The Grand Duchy's head of government condemns the lack of "concern for the others" among the Union's leaders. He said the states that will join the EU next May need a "European apprenticeship" to learn how to care about their partners.
The ten incoming countries have come under attack by EU officials for stubborn defence of their national interest during negotiations in the IGC.
But the Luxembourger insists the new members should not be criticized for that, as "this is also true for the old member states. Even among the 15 present EU members we all have an under-developed concern for the others." Juncker, who is tipped by many in Brussels as the successor to Romano Prodi as the head of the Commission, challenges those of his counterparts advocating one full commissioner per member state "to reflect on the consequences of this".
"I would personally like the Commission president to remain the game-maker in Europe. I would not like him to become a kind of linesman solely watching the respect of competition and internal market rules. "The Commission should be placed where the [EU's] central motor is. The best method to achieve this is to limit the powers of the European Council president and re-focus the Commission so as to allow it to decide with the intensity and efficiency required."
The College should comprise of one commissioner of all nationalities, he says, but not all should be allowed to vote.
The new member states should nevertheless have a commissioner with full voting rights during the first five years following their accession: "It is a matter of national dignity for them." Juncker brands as "illogical" member states' lack of trust in the Commission. "It is responsible before the [European] Parliament, it is not a submarine which can disappear and escape control."
The Grand Duchy's premier wants a strong Commission, but warns that the College should not be compared to a government.
"This gives bad ideas to commissioners and to those in national governments. People like being governed by a national government."
In a passionate plea for the boosting of Europe's defence, the prime minister of Luxembourg insisted that "this is not a putsch against the United States" of America.
"It is not a diversion organized within NATO. It is our desire to take our own defence interests more seriously."
Juncker, who together with the leaders of France, Germany and Belgium is at the forefront of efforts to beef up the Union's defence policy, opines that "there is a certain immaturity in the transatlantic relations". "We have lost the art of trusting one another. If we Europeans say that our intention is not to chase the Americans out of Europe, the United States must believe us."
A common European defence is one of the continent's oldest ambitions, he says, and not an idea born in the aftermath of the Iraq crisis, as many in Washington believe.
"It is not because we quarrelled over Iraq or because we sometimes find ourselves in political disagreement with the United States that we suddenly discover a new ambition which is defence. "No, this ambition is older than the [1957] Rome Treaty."