Former Labour spin doctor Alastair Campbell has attacked newspapers that support Britain quitting the EU for plumbing "fresh depths of dishonesty".
Tony Blair's ex-director of communications said "the wretched right-wing press" was becoming little more than "propaganda sheets".
In an article for the Observer, he also dismissed reports that the Queen backed Brexit as a "load of c**k".
"More than in any such debate I can remember, large chunks of the press have totally given up on the role of properly informing public debate," he wrote.
"The Mail, the Sun, the Express, and the Star in particular, to a lesser extent the Telegraph and, on a bad day, the Times, are more propaganda sheets for one side of the argument."
Justice Secretary Michael Gove is facing continued pressure over claims he was a source for reported comments made by the Queen on the EU.
During a Brexit campaign visit on Saturday he refused to deny being involved and told reporters he did not know where The Sun got "all" of its information.
Buckingham Palace has lodged a formal complaint with the Independent Press Standards Organisation (Ipso) about the report, which appeared under the headline Queen Backs Brexit.
"I don't know how The Sun got all of its information," Mr Gove said.
Conservative MP Sir Nicholas Soames said Mr Gove "will know the right thing to do" if he had made a misjudgment.
He told the Mail on Sunday: "Michael is a man of the highest integrity, and if on this occasion he has made a terrible misjudgment, I am sure he will know the right thing to do."
Courtiers are reportedly stepping in to prevent the Queen being pulled back into the EU referendum campaign.
A Whitehall official with links to the Palace and No 10 told The Sunday Times: "There's a concern and a need to draw the Queen back out of the political space."
Meanwhile US president Barack Obama is set intervene again in the referendum debate during a visit to Britain next month, according to the Independent on Sunday.
Downing Street said no visit had been announced and it would not comment on "speculation".