US whistleblower Edward Snowden has said becoming an "international fugitive" has been worth it because of benefits it has brought the public.

The ex-National Security Agency (NSA) worker, who released thousands of documents to the press, said progress had been made in the two years since then, and added: "The difference is that you get a different quality of government when they are accountable to the public."

Speaking by video live-link from Moscow to an event in London organised by human rights group Amnesty International he said: "It has been incredibly rewarding, incredibly gratifying. Although I can no longer see my family, I can no longer live in my home, I can no longer work with colleagues I respect, the things I've received personally, and we've all benefited from publicly, make it all worth it."

Asked where he saw himself in five years' time, he said: "I think the most liberating thing about burning your life to the ground, and becoming an international fugitive, or so I'm told, is that you no longer have to worry about tomorrow, you think about today, and for me that's been a great experience, I'm actually quite grateful for it."

He added, to laughter: "I've applied for asylum in 21 different countries, including western Europe, I'm still waiting for them to get back to me."

Newspapers around the world have published stories about government abuses, and courts had acted to stop them, he said.

The Government in the UK was trying to reform the laws in a very negative way, he said - "rather than preserving civil liberties, they are trying to limit it".

Surveillance methods being used around the world gave government a window into "anybody's life at any given time".

He asked: "Do we really want the Government watching everybody all the time?"

It had been proved not to work, he said - despite surveillance, the Boston Marathon bombing still took place.

"That's because we can collect everything and understand nothing," he added. "We are spending resources for no benefit in terms of public safety, and a real cost in terms of freedom and liberty."

Snowden was a contractor working in Hawaii for the NSA when he became uncomfortable with the level of intrusion the agency and its foreign counterparts, including Britain's GCHQ, were making into the lives of innocent civilians.

After raising the alarm with his superiors, he decided to blow the whistle and stole tens of thousands of classified files with the intention of showing them to the world.

He fled to Hong Kong where he met with journalists working for The Guardian, as well as documentary film-maker Laura Poitras, to co-ordinate a series of articles that would expose mass surveillance programmes such as the NSA's Prism and GCHQ's Tempora, which involve ''hoovering up'' vast volumes of private communications.

Once Snowden's identity was out, he fled to Russia, where he remains wanted by the US authorities.