After his famously blistering defence of the NHS, Michael Sheen has thrown his weight to another controversial issue - condemning the "full frontal assault" by government on the Freedom of Information Act.
The Welsh star said the public's right to know should "transcend the political rivalries and jostling that make up the daily cut and thrust of the Westminster bubble".
The comments come as a commission considers changes to the legislation, potentially including more charges for access to material.
Sheen, who has portrayed former Prime Minister Tony Blair on screen, wrote for the News Media Association: "The public right to know is a principle that transcends the political rivalries and jostling that make up the daily cut and thrust of the Westminster bubble.
"You don't need to look too far afield to find examples of nations where citizens are denied this right, and to see the consequences for those people.
"When the public right to know is not upheld, government, at both a national and local level, becomes opaque and removed from the very people it is meant to serve ...
"The consultation on the Freedom of Information Act, currently being undertaken by an 'independent commission' appointed by the Government, is nothing short of a full frontal attack on these principles.
"If the politicians and civil servants behind this assault get their way, then the right of you and I to understand the workings of our democracy will be seriously damaged.
"Newspaper journalism, whether local or national, has used FOI to hold the government to account on everything from MPs' expenses to staff shortages in the NHS.
"It is an essential medium for making sense of the wealth of information which the Freedom of Information Act provides access to."
Sheen's said a powerful FOI act was crucial to monitoring what the government does to the NHS.
In March, a video of him defending the NHS went viral.
In that speech, he said politicians were "sniffing around for markets to exploit, for weaknesses to expose"
He told a gathering of activists: "There are plenty out there who believe in grabbing as much as you can... They won't say it of course, they're too smart for that."
"For decades there has been a systematic undermining of [the NHS's] core values, this is beyond party politics... The Labour government arguably did as much damage as any Tory or coalition government, this is about who we want to be and what we believe is worth fighting for."
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Writing about the FOI Act, Sheen said he was a "passionate" campaigner, and "a strong NHS with the ability to provide excellent healthcare to citizens is particularly close to my heart", The Press Association reports.
"Without a strong FOI Act, it would be much harder for me and those like me to see and understand the effects of Government policy on this vital service," he said.
"That's why I am voicing my support for a strong FOI Act which should be extended and strengthened rather than weakened."
An FOI Commission spokeswoman said: "Freedom of Information is an area of considerable public interest and we want to hear the views of as many people as possible, which is why we have announced this public call for evidence.
"The Commission is an independent body, with no pre-determined view, and is interested in gathering as much objective evidence as possible on the questions posed in the call for evidence."