Theresa May will lay down the law to her Cabinet after a series of vicious leaks targeting Chancellor Philip Hammond.
The Chancellor has blamed the attacks on rivals opposed to his stance on Brexit, while one ministerial colleague accused Mr Hammond of trying to "f*** up" the process of leaving the European Union.
Meanwhile, Brexit negotiations in Brussels will continue, with senior officials set to begin trying to address the difficult issue of the Northern Irish border after the UK has left the single market and customs union under Mrs May's plans.
Mrs May used a speech at a Tory drinks party on the House of Commons' terrace to warn against "backbiting" and tell MPs to prepare for "serious business" after Parliament's summer recess.
Without a Commons majority, Mrs May will be forced to rely on DUP votes to get Brexit legislation through the Commons and she will require iron discipline from her own party to secure its progress.
At the regular Tuesday meeting of Cabinet, Mrs May will remind her senior ministers about the need for the sensitive meetings to remain private.
The attempt to instil Cabinet discipline comes after a series of newspaper headlines about Mr Hammond's comments at last week's Cabinet, culminating in a story quoting an unnamed minister accusing the Chancellor of trying to "f*** up" Brexit.
Mrs May's spokesman declined to discuss the content of the leaks, but told reporters at a regular Westminster media briefing: "Of course, Cabinet must be able to hold discussions of Government policy in private and the Prime Minister will be reminding her colleagues of that at the Cabinet meeting tomorrow."
According to newspaper reports, Mr Hammond was slapped down by the Prime Minister for saying that women could "even" become train drivers - a claim he denied.
A separate report said that he had told colleagues that public sector workers were overpaid compared with those in the private sector.
The Chancellor used a TV appearance on Sunday to accuse Cabinet rivals of trying to undermine his agenda for a "softer" business-friendly Brexit prioritising jobs and the economy.
But the Daily Telegraph quoted one minister as saying: "What's really going on is that the Establishment, the Treasury, is trying to f*** it up. They want to frustrate Brexit."
At a summer reception for Tory MPs on Monday night, Mrs May warned that infighting could result in Labour and Jeremy Corbyn winning power.
A senior Tory MP who attended the event said Mrs May told them to have a break over the summer but to be ready for "serious business" when they return to Westminster.
The Tory MP said Mrs May's message to the party was "no backbiting, no carping".
Amid reports of ministers trying to oust her, the Prime Minister told the gathering the "choice is me or Jeremy Corbyn", adding that "nobody wants that", according to the source.
The Prime Minister told her MPs, who fought a major campaign for the third year running after the 2015 election and 2016 EU referendum, to have a "proper break" but "come back ready for serious business" when Parliament returns in September after the summer recess.
The outbreak of leadership gossip and Cabinet leaks in recent weeks has been blamed by Justice Secretary David Lidington on too much "warm prosecco" at summer parties.
But at the Tory reception it was "all Champagne, no warm prosecco", according to the source, while MPs ate canapes including miniature portions of steak and chips.
Brexit Secretary David Davis, tipped as a potential successor to Mrs May, returned to Westminster after a brief visit to Brussels for the start of the round of negotiations on Monday.
The mood among the 98 British officials in Brussels involved in this round of talks, scheduled to end on Thursday, was said to be "determined" and a source said they had "covered quite a lot of ground".
Home Secretary Amber Rudd said that ministers had "frank and full discussions" at Cabinet, but said she found reports of infighting "perplexing".
"We have frank and full discussions and then we agree what the position is, and then we go out and deliver on it, which is how Cabinet should operate," Ms Rudd told ITV's Good Morning Britain.
Ms Rudd rejected suggestions that Mrs May had lost her authority as a result of the botched election, insisting: "She is respected by the Cabinet, she is our Prime Minister, we do have 54 more seats than Labour and we are getting on with the job in hand."
She dismissed former Michael Gove aide Dominic Cummings's description of Mr Davis as "thick as mince and lazy as a toad".
"David Davis is doing a great job," said Ms Rudd. "We all support him in Cabinet. He is out doing one of the most difficult jobs and I've been very impressed by how he has been handling it."
Responding to former PM David Cameron's suggestion that some ministers should be strapped to a raft and sent down a "very, very dangerous" river, Ms Rudd said: "I'm not too good at rafting, so I won't be volunteering for that."
She added: "I'm hopeful that after a holiday - whether rafting or otherwise - we can all calm down and get on with the job in hand."
Asked whether members of the Cabinet were seeking to undermine Mr Hammond because they regard his vision of Brexit as too "soft", Ms Rudd told Sky News: "The Cabinet is united in wanting to make sure that we deliver a Brexit that does protect the economy, that does protect businesses ... Philip Hammond has talked about that and he is absolutely right to do so.
"He and the Prime Minister have been discussing the fact that we may need to have a transition or an implementation phase of a fixed period. That will depend on the negotiations with the EU.
"Above all, even having that on the table as part of the considerations is set to reassure businesses and employers that there won't be a cliff edge in this negotiation and in the way we leave the EU.
"We want to make sure that we have a soft landing, that we protect jobs and businesses and employers to make sure that the economy of the UK remains robust."