The EU said Friday it was ready to work with Britain's re-elected Prime Minister David Cameron on his reform demands but said key principles including the freedom of movement were not up for negotiation.

Cameron, whose Conservatives won a shock majority, has pledged to hold a referendum on membership of the European Union by 2017 and wants changes to the bloc's treaties on issues including migration.

"I confirm that the four freedoms in the treaty are non-negotiable. They are non-negotiable because they are the essence of the EU," Margaritis Schinas, a spokesman for European Commission President Jean-Claude Juncker, told a daily briefing. 

"The European Commission stands ready to work constructively with the new British government, and, yes, President Juncker looks forward to meeting David Cameron soon."

He pointed out that Juncker had opened the door for "minor" treaty changes in comments last month but ruled out any altering of the four key treaty principles of free movement of goods, services, capital and people.

"First we want to see and receive the U.K. proposals on reform, and of course in the spirit of openness, friendliness and constructive spirit... we are ready to discuss those in our quest for a fair deal with Britain."

"Treaty change is something that is not that easy but it's also part of a longer-term perspective of how we organize the European Union."

(AFP)