Europe's nations may seem deeply divided, but on Britain's membership of the EU, opinion is united. Europe's Foreign Ministers have lined up to call the UK's potential departure a "disaster".
The speech led the front pages of newspaper websites from France and Germany to Sweden, with many containing dire political warnings that European leaders are losing patiences with Britain's desire to "cherry-pick" the terms of a European relationship.
El País and El Mundo, the two biggest newspapers in Spain, both opened their online editions with Cameron's referendum announcement.
Spain's Minister of Foreign Affairs, José Manuel García-Margallo, said this was “awful news” for the UK, who would get “isolated in a world dominated by regional integration”.
“To think in an United Kingdom competing alone in a world with the US, China, India or Brazil is really not understanding our times”, said the minister on a radio interview.
“I believe the British have played a dangerous game by feeding euroscepticism and Cameron now feels obliged to convene a referendum”, added García-Margallo.
The Foreign Minister believes that, might the UK leave the EU, it will “be a heavy blow” for its local and financial industry, that would become “little banks of insular scope”. He recognised, nevertheless, that it would not be good for the EU either.
France's Le Monde opened its report claiming Cameron had "finally yielded to the Eurosceptics".
The paper's Florentin Collomp remarked: "Many close to the Prime Minister, including Education Secretary Michael Gove are already bragging that they have no qualms about leaving the Union if London does not get succeed in imposing its vision of a Europe à la carte.
"But this poker game stakes on the tolerance of its allies, which already seems to be reaching its limit."
Before the speech, France's Foreign Minister Laurent Fabius, said his country would "roll out the red carpet for British businessmen" if Britain leaves the EU.
On German radio, European Parliament President Martin Schulz attacked Cameron, saying he was not offering constructive criticism.
"David Cameron wants the EU be reduced to the single market, but he doesn't want, for example, for us to combine our skills to tackle climate change."
Former German Foreign Minister Joschka Fischer told Süddeutsche Zeitung that an EU exit would be a "veritable disaster" for the UK.
Italy's Foreign Minister Franco Frattini also tweeted his hope that the UK does not leave the EU.
Sweden's tabloid Aftonbladet reported that a British exit would be "to Britain, Europe and Sweden's disadvantage. For Swedish part, we would lose an important partner in the EU, we are close to the UK on many issues, and it would be unfortunate for the Swedish political interests. The EU as a whole is losing a strong and important State.
"As the UK is one of the three heavy-weight countries in the EU, the whole Union hit hard by an exit.
"With Britain outside the EU would be a weaker Europe. It brings economic strength, military reach and credibility in international politics."