Financial pressure and the introduction of fast-paced new technology could combine to increase the risk of press intrusion and inaccuracy, according to a new report.
A survey for the Media Standards Trust found few people (7 per cent) trust newspapers to behave responsibly and three-quarters (75 per cent) believe papers frequently publish stories which they know are not true.
The trust's report, A More Accountable Press?, said job cuts and the desire to get stories on to websites as quickly as possible has reduced the number of opportunities for stories to be checked and edited.
It also called for urgent reform of the industry's existing self-regulation system, describing it as "insufficiently effective" and "largely unaccountable".
"Without urgent reform, self-regulation of the press will become increasingly ineffective at protecting the public or promoting good journalism," it concluded.
The trust, an independent charity, described "an industry under severe economic pressure" as circulation and advertising plummet.
It said investing in costly new technology has added to the financial strain.
"Journalists are expected to produce more material, for more platforms, in less time.
"In this environment there is an increased risk of inaccuracy.
"This can only exacerbate the low opinion of newspapers already held by most people."
A survey of more than 2,000 people found almost seven out of 10 (68 per cent) did not believe national newspapers could be trusted to behave responsibly.
Only one in 10 (10 per cent) agreed that editors could be trusted to ensure that their journalists act in the public interest compared with 69 per cent who disagreed.
More than half (58 per cent) said there should be more regulation of national newspapers and almost three-quarters (73 per cent) said the Government should do more to ensure newspapers correct inaccurate stories.
Seven out of 10 people (70 per cent) said there were "far too many" instances where people's privacy was invaded by newspaper journalists and 60 per cent of those surveyed said the Government should do more to prevent national newspaper journalists from intruding on people's private lives.
The report concluded: "Public trust in the press has fallen below the level necessary for it to perform its proper role in a democratic society.
"Until the system is reformed there is little chance of trust being raised.
"At a time of serious decline in newspaper sales, a renewal of public confidence would be as much in the industry's interests as in the public interest."
It said the Press Complaints Commission (PCC) "does not appear to take on an obligation more widely to monitor standards of the press, or to deal with non-compliance".
It said the PCC "initiates very little action" even when there seems to be "clear breaches" of its code of practice and tends to limit itself to mediating on complaints.
David Bell, chairman of the Media Standards Trust, said: "For quality journalism to survive - and avoid state interference - it must demonstrate why it is valuable to our society and critical to our democracy.
"For this to happen, it is essential that self-regulation opens itself up to scrutiny and makes itself accountable to the public."
PCC chairman Sir Christopher Meyer dismissed the report as "careless and shoddy".
"We are scrutinised by an independent charter commissioner, an independent charter compliance panel and all the way in which we organise ourselves is absolutely transparent," he told the BBC Radio 4 Today programme.
"Those two bodies... publish reports every year. I don't bowdlerise them, I don't censor them.
"And you will find on our website how people complain about how we deal with their complaint, you will see the commissioner's register of interests, you will see the panoply of committees that form the self-regulatory system, you will see our articles of association, you will see our complainants' charter.
"It is all there and if this trust had made the attempt to come to the PCC, take evidence from me, take evidence from my colleagues, they might have found this.
"The trouble is, unlike parliamentary committees, they don't come to the PCC and take evidence directly.
"Without this, this report is in effect a kind of scissors and paste job from the cuttings masquerading as a serious inquiry."
He added that the PCC had "record numbers" of people coming to it for help and advice.
"This has got to be seen as a vote of confidence in our ability to remedy complaints," he added.
The Media Standards Trust's review will continue with a consultation with the public, press, political representatives and those who have been involved with the PCC.
The self-regulation system will also be compared with those in other countries before recommendations are drawn up.
YouGov questioned 2,024 people in December 2008 on behalf of the trust.