Former senior WA Health bureaucrats face possible criminal charges after a major investigation uncovered one of the biggest corruption scandals in the State for decades.

The episode has prompted authorities to issue a broad appeal for public servants across government to come forward with information amid concerns contractors may be targeting other departments with corrupt practices.

The Corruption and Crime Commission dropped a bombshell report yesterday, alleging contractors lavished executives at the North Metropolitan Health Service with expensive meals, boozy lunches, overseas travel and even home renovations in return for scoring “tens of millions of dollars” worth of construction work.

Contractors won lucrative business on Sir Charles Gairdner Hospital, PathWest, Graylands Hospital, Midland and Joondalup health campuses, as well as work integrating Perth Children’s Hospital with the QEII site in Nedlands.

The CCC called for the prosecution of former NMHS executive director of facilities management John Fullerton, who the agency alleged had engaged in corruption with contractors for “years”.

Mr Fullerton, who took a voluntary redundancy from the department in 2016, was alleged to have had contractors renovate his home and his mother’s home, with fraudulent invoices billed to NMHS to cover a portion of the work.

It is alleged Mr Fullerton was offered or asked for other benefits in return for contracts, including overseas trips, tens of thousands of dollars in lunches and cash.

The CCC also called for the prosecution of Health bureaucrats David Mulligan and Shaun Ensor.

Investigators said Mr Mulligan, former executive director of the Perth Children’s Hospital integration, had arranged for contractors to win tenders to cover cash paid to him directly by Grant Alexander, a project manager to NMHS described as a “middle man” by the CCC.

The report said Mr Ensor, a former acting manager of facilities development, was “groomed” over expensive lunches to favour contractors. Mr Ensor left NMHS this year with a voluntary redundancy.

Health Minister Roger Cook said the Government would seek urgent advice from the State Solicitor’s Office on how to recover severance payments to those named as corrupt. The CCC also called for the prosecution of 10 contractors.

CCC Commissioner John McKechnie noted a number of those contractors performed work for other government departments, and he urged public servants with knowledge of other corrupt behaviour to come forward.

“I wonder if even now if there are heaps of public servants getting on the phone cancelling lunch dates,” Mr McKechnie said.

The CCC report criticised the Health Department, which the CCC had alerted to possible claims of corruption in 2014.

WA Health conducted its own internal investigation, but failed to take action against anyone.

“Warning signs were left unexplored,” the CCC report said. Investigators detailed how contractors had started to seek influence over other bureaucrats after word got out Mr Fullerton was taking a redundancy.

The report said $125,000 was spent on lunches for NMHS employees by contractors over 10 years and more than $150,000 was spent on travel for Mr Fullerton and Mr Mulligan.

“Regular and expensive gifts and gratuities given to some NMHS public officers were bribes,” the CCC said.

“Systematic manipulation of procurement practices was financial fraud.”

The CCC used surveillance and listening devices as part of its investigation and detailed how targets tried to destroy evidence once they discovered they were being watched.

The report said one contractor, Garth Delavale, spent $8600 on meals for Mr Fullerton between 2009 and 2016 at restaurants such as Matilda Bay and Galileo Buona Cucina.

Lunch appointments were always made by Mr Fullerton or his personal assistant, who would send an electronic meeting request. Mr Fullerton would select the alcohol.