As Premier Daniel Andrews marks his first year in power on Sunday, the government has unveiled reforms designed to strengthen the state's integrity system, which experts have warned is one of the weakest in the country.

The changes, to be introduced into parliament next week, will give the Independent Broad-Based Anti-Corruption Commission the authority to examine a new common law offence – misconduct in public office – and will reduce the amount of evidence IBAC must gather before an investigation can formally begin.

The Auditor-General will also get the power to "follow-the-dollar" on public-private-partnerships – enabling him to thoroughly put the microscope on future infrastructure plans such as the Metro Rail Project – while the Ombudsman's office will be revamped to give people more avenues to lodge complaints.

"These are very important changes and they will be delivered in full," Mr Andrews told The Sunday Age.

The Premier's comments come as his government marks its first anniversary on Sunday, exactly a year since the Napthine Coalition government became the first Victorian administration in almost 60 years to lose office after only one term.

In an interview reflecting on the past 12 months, Mr Andrews also:

•  Revealed he was surprised by the "great interest" coming from China to partner in the delivery of some of the government's infrastructure projects, saying that he would welcome such foreign investment.
•  Lashed out at the Coalition for altering Labor's same-sex adoption laws (the bill was amended to include religious exemptions) but signalled the government would accept the decision and not get "caught up in ideology".
•  Flagged an overhaul of executive bonuses across state departments in a bid to curb the number of senior bureaucrats getting lucrative rewards even when performance in services declines.
•  Nominated family violence, violent extremism and infrastructure delivery as some of key challenges he would face of the next 12 months.

The push to overhaul Victoria's integrity regime comes after a busy year for IBAC, which assessed 4443 allegations of corruption and misconduct within 12 months, finalised 15 investigations, and held its first public inquiries – including the so-called "banker schools" scandal, in which senior department officials were caught systematically rorting education funds.

But it also comes at a critical juncture for the integrity system, after two of its key watchdogs recently resigned under controversial circumstances.

In September, Auditor General John Doyle stood down only weeks before a damning review found he had sexually harassed and later bullied one of his female staff. A few months earlier, Victoria's inaugural Freedom of Information Commissioner Lynne Bertolini​ also quit after a government-commissioned report found a number of serious probity and management concerns within her office.

The government's changes are likely to be welcomed by experts, many of whom have spent years calling for the state's integrity regime to be strengthened.

"Victorians might not realise our state has the worst and least effective government integrity system in Australia," wrote former judge Stephen Charles, QC, in a recent column for the Fairfax press. "With no effective integrity system it is hardly surprising corruption has gone uncovered."

At present, IBAC has had to find prima facie​ evidence of a criminal offence before it can start an investigation, making it difficult for the watchdog to act on all the allegations it received.

And without follow-the-dollar powers, the Auditor-General's office has been unable to compel private companies, such as those engaged in public-private partnerships, to provide information. Last year, for instance, the audit office was unable to visit two private jails – Port Phillip Prison and Fulham Correctional Centre – while investigating drug use in the corrections system, because its mandate did not extend to private-sector providers.

"We have billions of dollars listed in the state's accounts for PPPs or outsourced contracts that the auditor general can't scrutinise. If they draft these legal powers correctly, then that is about to change," said Greens leader Greg Barber.

Opposition spokesman John Pesutto​ said establishing IBAC was one of the previous government's proudest achievements, and the Coalition went to the election also promising to expand its powers. He said the Liberals would examine Labor's proposals carefully.