The cost of setting up and running a Federal Independent Commission Against Corruption (ICAC) over the forward estimates would be similar to the cost of the government's trade union royal commission, according to a costing prepared by the Parliamentary Budget Office for the Greens.

Key points: Brickworks donated $150,000 to the Liberals before last election

Brickworks donated $150,000 to the Liberals before last election Company received $14.6 million of grants relating to the Clean Technology Investment Program, despite it being axed

Company received $14.6 million of grants relating to the Clean Technology Investment Program, despite it being axed Costings show a permanent Federal ICAC would cost roughly the same as Trade Union Royal Commission

The paper, obtained by 7.30, puts the cost at $47.5 million. The Trade Union Royal Commission cost $46 million.

A number of crossbenchers declined to back Monday night's critical Australian Building and Construction Commission (ABCC) vote unless it was broadened to include a federal ICAC, and the Greens are continuing to push for the body.

"Most Australians want to know that the huge vested interests that are corrupting Australian politics are exposed and that's why a watchdog like this is just so critical," Greens leader Richard Di Natale said.

Robert Wyld, the senior vice-chair of the International Bar Association's Anti-Corruption Committee, says there's a need for a federal ICAC.

"I think the union movement royal commission was certainly a one-off commission that was probably needed in that particular industry," Mr Wyld told 7.30.

"I think better funds are spent looking at society across all levels, particularly the government because it is involved in all industries, all sectors of the economy."

Government relationship with controversial donor in the spotlight

The Greens say the lack of a federal body to investigate the awarding of grants to Brickworks, a heavy Liberal party donor, shows the need for a federal ICAC.

NSW ICAC hearings in 2014 showed close links between the company and the Liberal Party.

Brickworks paid for a researcher in the office of former Premier Barry O'Farrell and may have breached laws preventing donations from property developers.

Prime Minister Tony Abbott tours a Brickworks factory in 2011

Mr O'Farrell said he was unaware the company was paying the researcher.

The company's premises were also used as a backdrop for former prime minister Tony Abbott's anti-carbon tax campaign and it discussed parliamentary tactics with Mr Abbott's chief of staff, Peta Credlin.

The Liberal Party received two donations from Brickworks totalling $250,000 on the eve of the 2013 election.

Following his election win, Tony Abbott scrapped the carbon tax and shut an industry compensation scheme called the Clean Technology Investment Program (CTIP).

That had an unintended consequence for Brickworks, with the company spelling out in its annual report that millions of dollars in grants were now in jeopardy.

"A further three projects totalling $14.6 million have been approved under the [CTIP] but are yet to have contracts signed," Brickworks' 2013-14 annual report said.

"With the change in Federal Government policy on carbon, it is unclear whether uncontracted projects under the CTIP will proceed."

The Government had no obligation to pay the grants but decided to honour all 106 projects that had not been signed off on, including the Brickworks grants.

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There is no evidence Brickworks received special treatment but Senator Di Natale said it should be investigated.

"We know they were the recipient of a significant grant, $17 million was the total. We know that $14 million came at the behest of the Abbott government, we know that the money was approved by the then Abbott government," Senator Di Natale told 7.30.

"We don't know whether what transpired was appropriate or whether it was part of the huge problem we've got in the Federal Parliament, which is these donations that are often done for favours from political mates," he said.

Grants initially approved by Labor: Brickworks, Coalition

In a statement to 7.30, Brickworks said the money funded good projects, initially approved under Labor.

Greens leader, Richard Di Natale, says that because their is no Federal ICAC we won't know whether the payments to Brickworks were appropriate.

It decided not to access all the money available and received $3.9 million after the scheme had closed.

"The grants were awarded on the basis that they delivered carbon abatement at a competitive rate," the statement said.

"The projects were innovative and involved both energy efficient plant and the substitution of fossil fuels by clean renewable fuels."

Former prime minister Tony Abbott did not respond to inquiries but a spokesman for the Industry Minister Christopher Pyne said all grants were initially approved by Labor.

"Brickworks' grant applications were treated in the same way as all other applications under the Program," the spokesman said.

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Government grants consultant Ben Cusack said the fact that the signing of contracts happened after the scheme had closed and there was no ongoing revenue from the tax was "very rare, very strange".

"It's quite strange when a government axes a program that it continues to fund applicants, certainly recipients after the program has closed," he told 7.30.

"Normally a grant is tied to the income that comes into it and certainly this one was tied to the carbon tax, so when the carbon tax stops coming in they have no further money to fund applicants."

NSW ICAC couldn't investigate Brickworks

Letters obtained by 7.30 show Greens Leader Christine Milne wrote to the NSW ICAC in September 2014 asking them to examine the grants as part of Operation Spicer.

The Commission replied it had no jurisdiction.

"While the Commission is unable to pursue the matter that have been raised because the circumstances of the awarding of Federal Government grants and its funding are outside the Commission's jurisdiction, I thank you for the information provided," wrote Deputy Commissioner Theresa Hamilton.

Robert Wyld says there is a gap between the Federal and State schemes and the government should consider introducing an anti corruption body based on the Hong Kong model.

"It investigates and it prosecutes, and that answers some of the criticism directed to the NSW ICAC because that only investigates and it shines a light into corruption but then it's somebody else's problem to look at a prosecution, and that's often where nothing happens."