Conservative in-fighting over the EU referendum has worsened amid reports the Foreign Secretary swore at a senior Eurosceptic colleague and David Cameron was warned he faces a plot to oust him as PM.

On Saturday night it emerged the Foreign Secretary, Philip Hammond, reportedly called Conservative MP Bill Cash “a total s***” after he defied orders to keep a report on the EU deal negotiated by David Cameron under wraps.

In a letter published by the Mail on Sunday, Mr Hammond is accused of explicitly telling him: "This is not a public document so while I will draw on it tomorrow we should refrain from referring to it explicity in the session."

The leaked document, written by the legal aide to the European Council president Donald Tusk, gave advice that the new settlement for Britain would be legally binding as if it were enshrined in a new EU Treaty – and could not be overturned.

Eurosceptic Labour MP Kate Hoey, who saw Mr Hammond’s outburst, said to the newspaper: "It was totally uncalled for. As we walked out of the committee room during an adjournment, Bill bumped into Hammond and went to make polite small talk like the gentleman he is.

"He said something innocuous like “Everything OK, Foreign Secretary?” Hammond glared at him, got right up to Bill’s face and hissed, “No, it isn’t! I told you that document was ‘Limité’ [French for ‘restricted’] and that you were not to distribute it. You deliberately ignored me; you are a total s***!

"Bill was speechless, and Hammond stomped off. It is hardly an appropriate way for a Foreign Secretary to behave. He is clearly rattled."

It comes amid claims the Prime Minister has been warned of a plot to oust him following the EU referendum if he fails to put a stop to Tory in-fighting and sniping.

What's the European Parliament ever done for us? Show all 5 1 /5 What's the European Parliament ever done for us? What's the European Parliament ever done for us? A cap on the amount of hours an employer can make you work The Working Time directive provides legal standards to ensure the health and safety of employees in Europe. Among the many rules are a working week of a maximum 48 hours, including overtime, a daily rest period of 11 hours in every 24, a break if a person works for six hours or more, and one day off in every seven. It also includes provisions for paid annual leave of at least four weeks every year Getty Images What's the European Parliament ever done for us? Helping the people of Britain to avoid smoking In 2014 MEPs passed the Tobacco Products Directive strengthening existing rules on the manufacture, production and presentation of tobacco products. This includes things like reduced branding, restrictions on products containing flavoured tobacco, health warnings on cigarette packets and provisions for e-cigarettes to ensure they are safe What's the European Parliament ever done for us? Helping you to make the right choices with your food Thanks to the European Parliament, UK consumers have access to more information than ever about their food and drink. This includes amount of fat, and how much of it is saturated, carbohydrates, sugars, protein and so on. It also includes portion sizes and guideline daily amount information so people can make informed choices about their diet. All facts must be clear and easy to understand What's the European Parliament ever done for us? Two year guarantees and 14-day returns policy for all products Consumers across the EU have access to a number of rights, from things which are potentially very useful, to things which used to be annoying. For example, shoppers in the UK receive a two-year guarantee on all products, and a 14-day period to change their minds and return a purchase, these things are useful www.PeopleImages.com-licence restrictions apply What's the European Parliament ever done for us? Keeping your air nice and fresh (and safe) Believe it or not, although the situation is improving, some areas of the UK have appalling air quality. A report by the Royal College of Physicians released on 23 February says 40,000 deaths are caused by outdoor air pollution in the UK every year. Air pollution is linked to a number of illnesses and conditions, from Asthma to diabetes and dementia. The report estimates the costs to British business and the health service add up to £20 billion every year

According to the Sunday Times ministers and senior backbenchers threatened a no-confidence vote unless Mr Cameron tones down attacks on Boris Johnson and other Eurosceptics.

Just 50 Tory MPs are needed to trigger a vote of no confidence in the leader - meaning just over a third of the 139 pro-Brexit Tory names would be needed to trigger a coup. A senior Tory MP told the newspaper: “Cameron's position will be untenable even if he wins the referendum if he carries on like this. There will be no problem getting 50 names.”

Last week, Mr Cameron made a less-than-subtle dig at Mr Johnson, saying: "I'm not standing for re-election. I have no other agenda than what is best for our country. I'm standing here telling you what I think.”

Mr Cameron also ridiculed Mr Johnson’s ambiguous suggestion in a recent newspaper column that voting to leave could lead to a better deal for Britain in Europe.“We should also be clear that this is a final decision,” he told MPs, arguing that a second renegotiation was “not on the ballot paper”.

“I won’t dwell on the irony that some people who want to vote to leave apparently want to use a leave vote to remain. But such an approach also ignores more profound points about democracy, diplomacy and legality.” The PM added that the idea that other EU states would give Britain more changes to EU structures was “for the birds”.

In a second altercation, George Osborne also launched a thinly veiled attack on the London Mayor Boris Johnson over his decision to back a leave vote – insisting that the decision was not “some amusing adventure into the unknown”.

His remarks came after Mr Johnson compared his own defiance of Brussels to James Bond. Mr Johnson pointed out in an interview that the most recent Bond film, Spectre, had been partly shot in his Mayoral offices, saying it was ‘where James Bond shoots the evil baddie who is hellbent on subverting democracy around the world through a supra-national organisation...I think there’s a metaphor there’.

On Saturday a poll for The Independent found that the campaign for Britain to leave the EU enjoyed an eight-poll lead when people’s likelihood to vote is taken into account.

Some 52 per cent of people said they would vote to leave, with 48 per cent saying they would back remaining, the exact opposite of last month’s findings. People were also asked how likely they were to vote in the June referendum on a scale of one to 10. When the figures were weighted, with a 10/10 score given a full percentage point and 9/10 given 0.9 of a point, the Leave total went up to 54 per cent and Remain fell to 46 per cent.