The chief executive of PwC Australia has resigned in response to a leak of confidential Treasury information on tax policy, a scandal that sparked a broader examination into the government’s use of consultants. Tom Seymour, whose resignation is effective immediately, was one of dozens of partners who received emails about confidential information obtained by former PwC adviser Peter-John Collins. The Tax Practitioners Board deregistered Collins last year after finding that he shared the confidential information obtained through consultations with Treasury. Sign up for Guardian Australia’s free morning and afternoon email newsletters for your daily news roundup Seymour had repeatedly apologised for the breach and recently told a Senate inquiry into the government’s use of consultants that the firm’s internal processes had been improved after the breach. “These findings have disappointed many of you in the parliament, as well as our regulators, clients, our partners and staff and the general public,” Seymour said in his submission to the inquiry. “Personally and on behalf of my partners, I apologise unreservedly for what occurred.” But the apology was not enough to secure his position. After discussions with PwC’s board of partners on Monday, Seymour’s resignation was announced in a short statement. “We agreed with Tom that this is in the best interests of the firm and our stakeholders,” the PwC statement said. Tracey Kennair, the chair of PwC Australia’s board of partners, said the firm needed to immediately rebuild trust with government and the public. “The independent review previously announced, in addition to the changes already made, will help us meet this objective.” The acting chief executive, Kristin Stubbins, said the firm was committed to learning from its mistakes and building a stronger culture of trust and transparency. The Greens had called for Seymour to resign and for PwC to be banned from all new government contracts as a result of the tax policy breach. “This is not an organisational culture you want to contract with,” Greens senator Barbara Pocock said. “There is a dire need for transparency and accountability in the consulting industry and these latest revelations only make the need for reform more urgent.” When the breach was first revealed, treasurer Jim Chalmers said he was “absolutely furious and absolutely ropeable about the revelations”. “There is no consultation without trust,” he told reporters in Canberra. “We want to be able to consult in a meaningful way when changes to the tax system are in prospect. “And the actions that we’ve seen alleged and reported cut across that … this puts that sort of consultation at risk. The PwC breach has triggered another examination into the government’s use of consultants, with former public servants and independent experts warning conflicts of interest are rife. The federal government has become increasingly reliant on consultants to perform the work of public servants, with an audit revealing the government spent $20.8bn on external experts in just one year. Many of the biggest consultancy firms are paid by the government to work with confidential information, while simultaneously charging businesses in the same sectors for strategic advice.