Boris Johnson has warned senior members of his administration against bullying, leaking, or trying to frustrate Brexit, as he published a new edition of the ministerial code of conduct.

Theresa May’s cabinet was described as “the worst example of ill-discipline in cabinet in British political history”, by Julian Smith, her own chief whip and the man responsible for keeping his colleagues in order.

In a foreword to the code of conduct, published on Friday, Johnson said his ministers would “uphold the very highest standards of propriety”. “There must be no bullying and no harassment; no leaking; no breach of collective responsibility. No misuse of taxpayer money and no actual or perceived conflicts of interest,” he said.

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Johnson also warned against “misuse of process or procedure by any individual minister that would seek to stall the collective decisions necessary to deliver Brexit and secure the wider changes needed across our United Kingdom”.

May’s government was repeatedly rocked by splits and rebellions, even at cabinet level by the so-called Gaukeward squad of ministers – which included the former justice secretary, David Gauke – who were determined to prevent a no-deal Brexit.

Johnson dispatched most of the culprits to the back benches when he assembled his own team in July, but is keen to send a signal that he will not tolerate fresh outbreaks of dissent. His senior adviser Dominic Cummings, the former Vote Leave campaign director, has stressed the need for discipline, reportedly telling Tory aides that Brexit must be achieved “by any means necessary”.

Johnson’s plea for good behaviour comes after he rehabilitated Gavin Williamson, who was sacked by Theresa May after allegedly leaking details of discussions about the Chinese telecommunications company Huawei and is now the education secretary. May said at the time that an investigation by the cabinet secretary, Mark Sedwill, had uncovered “compelling evidence” that Williamson was responsible for revealing the sensitive row to a journalist at the Daily Telegraph.

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Priti Patel, who resigned as the development secretary after setting up unauthorised meetings with Israeli officials, has also been brought back into cabinet by Johnson. And the prime minister also dropped a Whitehall investigation into Mark Field, the Tory MP who was caught on camera manhandling a Greenpeace activist out of a black-tie dinner. Field was a minister at the time of the incident, but was not given a post in Johnson’s government. The prime minister’s spokesperson said Field’s conduct was a matter for May.

In his foreword to the code of conduct, Johnson said his government’s “mission” was to deliver Brexit on 31 October “for the purpose of uniting and re-energising our whole United Kingdom and making this country the greatest place on earth”.

He is also announcing £125m of new taxpayer funding to support new, greener transport technologies on Saturday. Backed by £175m of private sector support, the investment will be used to help develop proposals, including flying taxis and freight-carrying drones, the government said.

As part of the package, five transport research networks at universities will receive £5m each to work on cleaner fuel and other innovations.

Johnson said: “This £300m investment will help speed up the development of greener flights, and new ways of delivering the goods we order online.

“The UK is already recognised around the world as a centre for green tech. Now we will lengthen our lead, supporting our industry and our citizens to reduce their carbon footprint.”