Addressing the European Parliament in Strasbourg today (Wednesday), Junker told MEPs that the renegotiation settlement unveiled by European Council President Donald Tusk on Tuesday was fair for all sides.
In spite of the fact that the British Prime Minister David Cameron had actively campaigned against his appointment as European Commission chief, Juncker said that he had been, "working closely with both Tusk and Cameron to shape the proposal presented yesterday."
"I've always said that I wanted the UK to remain a member of the EU on the basis of a fair deal," said Juncker, adding; "The proposed settlement is fair for the UK and fair for the other 27 EU member states."
Junker told MEPs that Tusk's proposals clearly acknowledged British concerns over closer political union, saying; "The UK benefits from more protocols and opt-outs than any other member state. This is why, as a matter of law and as a matter of fact, the concept of 'ever closer union' has already assumed a different meaning".
The new settlement, said Juncker, "recognises that if the UK considers that it is at its limit on levels of [EU] integration, then that is fine. At the same time, it makes clear that other member states can move towards a deeper degree of integration as they see fit."
On the thorny issue of British demands for economic protection from discriminatory financial laws by Eurozone members, Juncker said that it was "legitimate" to allow non-Eurozone member states [such as the UK], "an opportunity to go to the European Council if they think that the principle of non-discrimination might have been violated. It is legitimate for those member states not to have to have financial responsibility for measures taken to guarantee the stability of the Eurozone."
Juncker acknowledged that the most challenging aspect of Cameron's renegotiation demands had been the issue of free movement and restricting in-work benefits for newly arriving EU migrants.
He said that the proposed emergency brake safeguard was, "tailor-made" to address British concerns, would apply only in "exceptional" circumstances and, crucially, was also "compatible with the [EU] treaties", therefore allowing London to restrict access to in-work benefits for a period of up to four years.
"The duration of the mechanism will be time-limited in time. That's a crucial characteristic of a safeguard mechanism, necessary in order to make it compatible with the treaties."
Juncker also appeared to suggest that the impact of Britain's decision back in 2004 not to, "use the transitional periods that would have allowed it to phase in the right of free movement of the citizens of eight new member states," constituted an exceptional circumstance.
"As a result, over the past decade, the UK has attracted a record number of mobile new citizens. In effect, we will enable the UK to use the safeguard mechanism to address the consequence of that decision," said Juncker.
Two weeks of intense talks now lie ahead, as so-called Sherpas and negotiators on both sides look to agree a deal that can be officially rubber-stamped by EU leaders at their summit on 18-19 February.
An agreement at that meeting would pave the way for a British in-out referendum in the early summer, potentially on Thursday June 23.