Lord Prescott has resigned from the Privy Council in protest against delays to changes in the way the press will be regulated in future.
In the Sunday Mirror, the Labour peer said the hold-up was a "political" choice that "borders on conspiracy".
Ministers insist the Privy Council must consider a cross-party royal charter to underpin a new system of regulation after a rival charter from the press.
But "Parliament's charter" should be considered first, Lord Prescott argued.
'Conflict' with monarchy
The Privy Council had been due to consider proposals agreed on by politicians and campaigners.
But according to the government, legal advice means the press's plans must be considered first because its charter was the first to be formally submitted.
Lord Prescott rejected this explanation.
"The government dragged its feet in further consultation and the press industry put in its divided charter first," the former deputy prime minister wrote in his column.
This was "clearly a political decision by the government", he said.
The proposed approach could mean that the Privy Council would not reach a final decision on the merits of the two alternative press regulation charters until January 2015.
If the charter backed by the three main parties in Westminster were not then approved, the matter would "be referred back to Parliament, four months before the next general election", said Mr Prescott.
The whole process could even "embroil the monarchy in a possible conflict with Parliament and political division between the parties", the Labour peer warned.
He concluded: "I have resigned as a Privy Councillor on this point of principle about how the charters are considered."
In November, the landmark Leveson report called for an independent regulatory body to be established to oversee the press, backed by legislation.
It followed an 18-month public inquiry into the ethics of the press, set up in the wake of the phone-hacking scandal.
The leaders of the three main political parties agreed to set up a new watchdog by royal charter with powers to impose million-pound fines on UK publishers and demand upfront apologies from them.
But the newspaper industry rejected the idea of "state-sponsored regulation", putting forward a plan with a series of key differences.
The newspapers' rival press royal charter would:
- Remove a ban on peers and former editors serving on the newly created "recognition panel", which will decide in future whether newspapers are being regulated properly
- Remove Parliament's power to block or approve future changes to regulation. Instead the regulator, trade bodies and the recognition panel would have to agree to changes
- Make it more difficult to bring group complaints
- Give the regulator the power to "require", rather than "direct", the nature, extent and placement of corrections, and abandon the idea of giving it the power to force newspapers to publish apologies
On Wednesday, Prime Minister David Cameron told MPs the government remained committed to the cross-party proposals despite the delay, and criticised "serious shortcomings" in the industry's charter.
The BBC understands that the Privy Council, which is is due to meet on 10 July, will not decide on the matter until the autumn at the earliest, since it is not due to meet again over the summer.
It is a very rare step to resign from the Privy Council, an ancient advisory body to the Queen of which membership is for life.
Privy Councillors are entitled to describe themselves as "right honourable".
History records just five others who have voluntarily left the group, the most recent of which was ex-cabinet minister Chris Huhne - who was jailed after pleading guilty to perverting the course of justice.
Lord Prescott is the first to quit the body in protest about its procedures.