A Labour government would give citizens access to policy-making processes "at every level", deputy leader Tom Watson has promised, as he accused David Cameron of trying to avoid public scrutiny and "govern from the shadows".
In a speech in London, Mr Watson called on the Government to scrap its review of Freedom of Information (FOI) legislation, which he said was "predestined" to end up significantly weakening citizens' rights to know.
Labour would instead "strengthen and extend" the FOI Act, said Mr Watson, arguing that "only in the most exceptional circumstances should state actions, from the biggest to the very tiniest thing, be protected from public scrutiny".
Mr Watson accused Mr Cameron of heading a "fundamentally illiberal" Government which had abused its power "as none has ever done before".
He cited Government moves to limit unions' powers to call strikes, slash state funding for opposition parties, strip the House of Lords of the power to block secondary legislation, give security agencies snooping powers without judicial oversight and rewrite the Ministerial Code to remove references to international law and treaty obligations.
And he said that the Government's efforts to avoid scrutiny were highlighted on Thursday, when more than 400 official documents were released almost simultaneously as the House of Commons broke up for the Christmas recess in what he described as "David Cameron's 'take out the trash' day".
Mr Watson added: "By publishing 36 written ministerial statements and 424 government documents in one day, they hoped that hard-pressed lobby journalists would miss the revelation that three-quarters of those affected by bedroom tax have cut back on food, according to the Department for Work and Pensions, that there has been a 45% rise in the number of homeless families living in emergency B&Bs, and that the Government has lost contact with 10,000 asylum seekers."
Accusing Mr Cameron of "the arrogance of power", the Labour deputy leader said Conservatives were actively trying to limit accountability "wherever they can".
"At every turn, they shrink from the light of transparency and retreat into the shadows," he said.
And he warned that the consequences of the Government's actions could be to "unknit the ties that bind our civil society together".
"With this administration, we are moving to a new era of private government, where ministers know best," warned Mr Watson.
Former head of the civil service Lord Kerslake last week dismissed claims that the FOI Act had a "chilling effect" on civil servants, insisting that the greater challenge to Whitehall's operations was the "routine" leaking of information by special advisers and ministers.
And the Commission, set up by Mr Cameron to review the Act's operation - which includes former home secretaries Jack Straw and Lord Howard - has come under fire for not including any freedom of information campaigners.
Mr Watson said: "I am calling on David Cameron today to abandon the review.
"It doesn't have the support of the public. It is opposed by many of the organisations that are covered by FOI. It has been condemned by the Information Commissioner and slammed by a former head of the civil service. It's a waste of taxpayers' money.
"The Freedom of Information Act works well. Labour would strengthen and extend it."
He added: "A future Labour government must provide citizens access to, and influence on, policy-making processes at every level."
Mr Watson said that the character of the current administration was driven by the personality of a Prime Minister who "doesn't like being challenged... reacts badly when confronted by an opposing point of view" and has an "instinct that his own opinion must always prevail".
"The Cameronian offer: 'Just leave it to us - trust us to sort it out even though we let you down last time' - won't cut it any more," said the Labour deputy leader.
"The offer needs to be: every aspect of what we do in your name is open to scrutiny. There is nothing to hide. We understand that if we don't want you to know about it, we shouldn't be doing it ."
Mr Watson insisted that "a more open government will be a better government, with more robust policy-making".
And he said that this will be all the more important over the coming quarter-century, when technological developments are likely to lead to new forms of state intervention in ordinary people's lives which will require new safeguards to protect citizens from erosions of their civil liberties.
Mr Watson declared: "Labour must say: 'No, Mr Cameron, we do not trust you. You must show us what is happening. Turn the lights up, not off.'"
Mr Watson said he had initially been "quite excited" by Mr Cameron's promise of a "new age of transparency" in 2010.
But, he added, "they have kind of put that into reverse gear" since taking office.
"If he (the Prime Minister) really wants to be a great statesman he should open himself up to greater scrutiny, and all the bits of government, instead of closing down the shutters," Mr Watson said.
The Labour deputy leader said there was a culture of secrecy in some areas of governance, including in local councils.
"Some of the best councillors I know, some of whom are cabinet members of local authorities, actually use the Freedom of Information Act to find out what's going on in their own authorities," he said.
"It does say something about the culture in local authorities when elected representatives feel they have to use the Freedom of Information Act to find out what's going on."
Jonathan Isaby, chief executive of the TaxPayers' Alliance, said: "Moves to dilute Freedom of Information are misguided and dangerous, so it's welcome news that Tom Watson is keen to protect it.
"It is every citizen's right to know how their money is spent and how decisions are taken in their name, so the Government should immediately drop its plans to weaken the Act.
"Power should be in the hands of taxpayers, not the politicians and bureaucrats who spend their money."