The incoming chair of Transparency International Australia has called on the government to urgently address its “shocking” loss of public trust by setting up a federal integrity commission and reducing the influence of lobbying and donations.

The barrister Fiona McLeod brings considerable experience to her new role as chair of Australia’s most prominent anti-corruption group. She led the federal government’s legal team during the child abuse royal commission, and previously represented the commonwealth in the Queensland floods inquiry and the 2009 Victorian bushfires royal commission. McLeod has also acted for the plaintiffs in the Don Dale class action.

McLeod told Guardian Australia her priorities at Transparency International were campaigning to fix the lax regimes governing lobbying and political donations, which she said “can and do result in decisions that can benefit business and powerful individuals rather than the public interest”.

“Rebuilding trust and confidence in government institutions and political processes is urgently needed,” she said.

Trust in government is at an all-time low. Transparency International’s recent global corruption barometer showed 56% of Australian respondents reported that they had witnessed or suspected favourable treatment from government in exchange for donations or support. About 85% said they believed some, most or all federal members of parliament were corrupt – nine percentage points higher than the year before. Less than half of respondents expressed a “great deal” or a “fair amount” of trust in federal and state governments.

McLeod said: “This is shocking and must be addressed if Australia is to reestablish its global leadership as a country that demonstrates strong democratic institutions and good governance, particularly in our dealings with countries that are conflict-prone and can have weak governance.”

She said a federal integrity body – wide-ranging, well-resourced, powerful and independent – was critical to combating bribery and corruption. McLeod said she hoped the Coalition was serious about strengthening federal integrity measures, but said its commitment to establish a federal anti-corruption agency “remains to be seen”.

“Clearly this is what the public wants and it is likely to be an election issue.”

McLeod also warned that stronger measures were needed to check the integrity and character of multinationals tendering for government work. Earlier this year, Guardian Australia revealed that foreign aid contractor Sinclair Knight Merz continued to be handed government contracts even after allegations of widespread bribery emerged against it.

“A ‘debarment’ regime should exist for those convicted of bribery and corruption in all Australian tender processes,” McLeod said.

Oversight of lobbying in Australia is another priority. Guardian Australia revealed last month that 52% of all registered lobbyists had previously worked inside government or party structures. One in four had previously staffed the offices of politicians.

A separate study by the Grattan Institute found one in four ministers or assistant ministers went on to lobby or work for special interests once they left parliament.

McLeod said the current cooling-off periods, which bar former ministers and parliamentary secretaries from lobbying in their portfolio area for 18 months, were not being enforced. Real-time disclosure of donations was also needed to ensure genuine transparency.

“We need better regulation and oversight of lobbying, in particular industry influence and the revolving doors between industry and government,” McLeod said. “We have some cooling-off periods but this appears to be poorly enforced.

“The revolving door between industry and politics, the lack of transparency of political donations – these are corruption risks.

“A process is only as strong as its weakest chain, and these weaknesses in our system risk undermining the national interest.”

McLeod replaces Anthony Whealy, a retired New South Wales supreme court judge, in the post.

• This reporting is supported by the Susan McKinnon Foundation through the Guardian Civic Journalism Trust