Traces of a suspected class A drug were found at a government grace-and-favour home after parties attended by political allies of Liz Truss, the Guardian has been told. The white powder was discovered at the Chevening estate last summer in the days before Truss won the Tory leadership contest and became prime minister, according to sources. A member of staff claimed they tested the powder using a swab which changes colour when it comes into contact with cocaine, and it indicated the drug was present. Possession of cocaine is a criminal offence which can lead to imprisonment for up to seven years, or an unlimited fine. In July, the government launched a new crackdown on casual drug users, saying their passports could be confiscated. Separate sources have described finding similar deposits in the offices at No 10 Downing Street after two lockdown parties held when Boris Johnson was prime minister. Staff working at Chevening claim on two occasions they found traces of white powder on a side-table in a games room with a snooker table, after nights where Truss was known to have entertained guests at the Kent country house, a retreat for foreign secretaries. Truss, then foreign secretary, hosted a gathering at the 17th-century Grade I-listed home during the weekend of 19-21 August as her leadership campaign was in full swing. Another gathering took place during the weekend of 2-4 September. A range of political allies were in attendance for both weekends. Chevening is a grace-and-favour home set in 3,000 acres. Use of the 115-room mansion is traditionally granted to the foreign secretary, and its upkeep is funded by a trust established by an act of parliament. An insider said cocaine was widely used across Whitehall and the parliamentary estate, and claimed that some of Truss’s political allies used it. There is no suggestion that Truss or Johnson themselves used the drug or that they would have been aware if drugs were used or present. The Guardian has not been told who was responsible for the alleged deposits of white powder. Truss lasted just 45 days as prime minister. The mini-budget presented by her then chancellor, Kwasi Kwarteng, in late September sent UK government bond markets into freefall and forced the Bank of England to spend billions of pounds buying government debt to protect market stability. Separately, sources who worked in No 10 during Johnson’s tenure claimed white powder residue was found after two parties held at the office complex despite Covid-19 restrictions. Johnson is understood not to have been at either party. White powder residue was found the morning after a party at No 10 on the eve of Prince Philip’s funeral on 17 April 2021, sources said. The Guardian has been told that cleaning staff found deposits of white powder in bathrooms and on a table in No 10 offices. Small plastic bags were said to have been discovered near the table on the floor next to the bin, together with tissues stained with spots of blood, and vomit. Sources also said there was evidence of a smudged line of powder and a discarded Boots Advantage card on the same table. It is not known who the card belonged to. Revelations about that party, held just hours before the Queen had to mourn alone at her husband’s funeral because of social distancing rules, caused outrage. They included reports that a suitcase of wine was wheeled to Downing Street and that a garden swing for the prime minister’s son was broken. Traces of white powder and small plastic bags were also found on 19 December 2020, the morning after a Christmas party, in the bathrooms at No 10’s office complex, according to sources. Staff suspected the material was likely to be traces of drugs as it was found amid wider evidence of partying including bottles, empty cans, and food wrappers. A separate source with knowledge of the parties claimed they were aware of drug-taking at both events. A senior civil servant, Sue Gray, was tasked with producing a report into lockdown-busting parties in No 10 and across Whitehall. There was no mention of drug-taking in her report. The Guardian’s revelations come after evidence of cocaine use in toilets next to Johnson’s then parliamentary office and several other locations across the parliamentary estate was reported last year. Johnson’s government put forward a drugs strategy that proposed that middle-class drug users could have their passports and driving licences confiscated, in order to “interfere” with their lives. During her brief tenure as prime minister, Truss’s spokesperson said that “cracking down on illegal drugs” was a priority. The Guardian put a series of questions to Truss about the claims regarding Chevening. She declined to comment in detail. A spokesperson for her said in a one-line statement: “This is categorically untrue.” After publication, her spokesperson added: “If there were evidence that this alleged activity had occurred during her use of Chevening, Ms Truss would have expected to have been informed and for the relevant authorities to have properly investigated the matter. As it is, the Guardian has produced no evidence to support these spurious claims.” The Foreign Office declined to comment on the allegations about activities at Chevening. A spokesperson for Boris Johnson said: “Boris Johnson is surprised by these allegations since he has not previously been made aware of any suggestions of drug use in 10 Downing Street and as far as he is aware no such claims were made to Sue Gray or to any other investigators. “It was a feature of Mr Johnson’s premiership that he strongly campaigned against drug use, especially middle-class drug use. His government made huge investments in tougher policing to help roll up county lines drugs gangs, which cause so much misery. He repeatedly called for harsher punishments for the use and distribution of class A drugs.” A spokesperson for No 10 said: “The Guardian has provided no evidence to support these claims. If there were substantive claims, we would expect these to be reported to the police. “There was an independent investigation into the nature of the gatherings under a previous administration – and its findings were published. That information was also handed to the Metropolitan Police Service who conducted their own investigation at the time.”