Kate Maltby, the Tory activist who made allegations of inappropriate behaviour against Damian Green, believes that his allies orchestrated a ferocious media onslaught in order to discredit her.

The Observer understands that the Whitehall inquiry that led to the de facto deputy prime minister’s sacking last week was handed material, seen by Maltby, which suggested Green’s supporters fuelled negative articles about her after she made her claims.

It has emerged that text messages between Maltby and Green, some apparently edited to suggest she had been pushing for a meeting with the former minister, had ended up in the hands of the media.

She told the Sunday Times that only Green or his allies could have leaked the material. However, Green and his closest aides deny any suggestion that they contributed in any way to the attacks on Maltby or passed on the texts. Maltby is understood to believe that collusion between Green’s allies contributed to an article in the Daily Mail headlined “One very pushy lady”.

The claims of inappropriate behaviour made by Maltby were eventually judged “plausible” by the Cabinet Office inquiry into the first secretary of state’s actions. Green ultimately lost his job after admitting that he had lied about the fact that pornography was found on his parliamentary computer during a police investigation in 2008.

May now faces the prospect of replacing Green, who had chaired a series of sensitive Brexit cabinet committees. Senior government figures on both sides of the EU referendum debate pointed to David Lidington, the justice secretary and former Europe minister, as the “ultimate safe pair of hands” who could do the job without upsetting Remainers or Brexiters.

Opinion is split among senior Tories over whether May should make the changes as part of a major reshuffle next month. It has not gone unnoticed by party whips that the main troublemakers for May have been former ministers such as Anna Soubry, Nicky Morgan and Dominic Grieve.

The latest twist in the affair comes as debate still rages over the role of the two police officers, Bob Quick and Neil Lewis, who were involved in Scotland Yard’s 2008 investigation into Home Office leaks. The investigation led to Green’s arrest and seizure of his parliamentary computers. It was during the course of that inquiry that online pornography was discovered. Green had denied any knowledge of the existence of the material, but has now admitted that his denial was misleading.

The College of Policing, which sets standards for serving officers through an official code of ethics, said that it expected the ethical code that the two officers signed in connection with their policing career to be upheld after they depart the force.

The code states: “I will treat information with respect, and access or disclose it only in the proper course of my duties.” It also makes clear that officers must “access police-held information for a legitimate or authorised policing purpose only” and “not disclose information, on or off duty, to unauthorised recipients”.

The College of Policing told the Observer: “We expect that members of the profession will be proud to maintain the standards contained in the code of ethics in relation to their policing career, after retirement.”

However, senior police sources believe there is a whistleblowing defence for Quick and Lewis, arguing that they acted in the public interest to highlight inaccurate statements made by a senior public employee. Sources also say there is significant support for the two officers.

Georgina Halford-Hall, chief executive of WhistleblowersUK, said: “It raises really serious issues about when people have information, who they disclose it to, how they should disclose it and how they should be treated.”