State Department spokeswoman Marie Harf said: "The notion that we were somehow trying to foment unrest … nothing could be further from the truth."

But Max Lesnik, a Miami radio commentator who supports the government of ruler Raul Castro, called Zunzuneo "an operation aimed at changing the Cuban government, regime change. This is a covert aggression through social networks."

The investigation found that the network was built in 2009 with secret shell companies and financed through a foreign bank. The project, which lasted more than two years and drew tens of thousands of subscribers, sought to evade Cuba's stranglehold on the internet with a primitive social media platform.

First, the network was to build a Cuban audience, mostly young people. Then, the plan was to push them towards dissent.

Yet its users were neither aware it was created by a US agency, nor that American contractors were gathering personal data about them, in the hope that the information might be used someday for political purposes.

It is unclear whether the scheme was legal under US law, which requires written authorisation of covert action by the president as well as congressional notification.

Carney said he was not aware of individuals in the White House who had known about the programme.

Josefina Vidal, of Cuba's foreign ministry, said on Thursday that the Zunzuneo programme "shows once again that the United States government has not renounced its plans of subversion against Cuba, which have as their aim the creation of situations of destabilisation in our country to create changes in the public order and towards which it continues to devote multimillion-dollar budgets each year".

"The government of the US must respect international law and the goals and principles of the UN charter and, therefore, cease its illegal and clandestine actions against Cuba, which are rejected by the Cuban people and international public opinion," the statement said.