American intelligence leaker Edward Snowden on Tuesday declared his "mission accomplished" after unveiling huge US surveillance programmes, but urged citizens to insist their governments stop spying on them. In his first major media appearances since claiming asylum in Russia, Snowden -- who sent shockwaves around the world by revealing the extent of Washington's electronic eavesdropping -- issued a staunch defence of individual privacy. The former National Security Agency (NSA) contractor is to deliver a Christmas Day broadcast on British television, calling on citizens to work together to end mass surveillance, Channel 4 said on Tuesday. "Together we can find a better balance, end mass surveillance and remind the government that if it really wants to know how we feel, asking is always cheaper than spying," he says in extracts released by the TV station. The short, pre-recorded broadcast will be Snowden's first television appearance since arriving in Moscow in June. The 30-year-old has also given his first in-person interview since claiming asylum, telling Tuesday's Washington Post: "I already won. "For me, in terms of personal satisfaction, the mission's already accomplished," he said. "As soon as the journalists were able to work, everything that I had been trying to do was validated," he added. "Because, remember, I didn't want to change society. I wanted to give society a chance to determine if it should change itself." Snowden leaked explosive details of the secret surveillance schemes to the Washington Post and Britain's Guardian and fled the United States. He arrived in Russia in June as a fugitive and spent more than a month holed up in a Moscow airport before being granted a year's asylum. US federal prosecutors have filed a criminal complaint against Snowden, charging him with espionage and felony theft of government property. His leaks have deeply embarrassed President Barack Obama's administration by revealing the massive scale of America's spying efforts, including on the country's own allies such as German Chancellor Angela Merkel. In his Christmas Day broadcast to Britain, Snowden says that children born into today's world will "grow up with no conception of privacy at all". "They'll never know what it means to have a private moment to themselves -- an unrecorded, unanalysed thought," he says in the broadcast, due to be aired at 1615 GMT. "And that's a problem because privacy matters. Privacy is what allows us to determine who we are and who we want to be." He signs off the broadcast by wishing Britons a merry Christmas. Channel 4 has aired a short "alternative" Christmas message every year since 1993, intended as a response to Queen Elizabeth II's annual Christmas Day broadcast on the rival BBC. The channel caused a political row in 2008 when it chose former Iranian president Mahmoud Ahmadinejad as its Christmas broadcaster. 'Not trying to bring down NSA' The NSA's collection of communications data has grown dramatically since the September 11, 2001 attacks. On Friday, Obama said he welcomed a debate about the NSA's role as he weighs possible changes to its broad powers amid a public outcry over rights to privacy. The president said he would make a "pretty definitive statement" in January about how the NSA should be overhauled. A panel of legal and intelligence experts chosen by the White House has recommended curbing the agency's powers, warning that its sweeps in the war on terror have gone too far. And a federal judge has warned that the NSA's routine collection of nearly all Americans' phone records was probably unconstitutional. Snowden insisted in the Post interview that he had not been disloyal to his former employers. "I am not trying to bring down the NSA, I am working to improve the NSA," he said. "I am still working for the NSA right now. They are the only ones who don't realize it." The leaker said it had been lawmakers' decision to keep the NSA programmes hidden and their failure to ask probing questions that entitled him to spill the secrets. "The system failed comprehensively, and each level of oversight, each level of responsibility that should have addressed this, abdicated their responsibility," he said.