TWU boss Tony Sheldon has told a royal commission the union’s fighting fund has been used legitimately in an environment where it’s much needed.

The boss of the powerful Transport Workers Union (TWU) has staunchly defended a union fund used to oust a branch secretary and interfere in other unions’ elections.

Before, during and after his appearance at the Royal Commission into Trade Union Governance and Corruption, Tony Sheldon said the McLean Forum Ltd was legitimate and he questioned the need for the government’s $52 million hearing.

Mr Sheldon, who is also a vice-president of the ALP, said such fighting funds were needed to counter a federal government who was dancing to the tune of big business.

He gave as an example “safe rates” legislation which would have increased rates for self-employed drivers, but was withdrawn after opposition from Coles.

Jeremy Stoljar SC, counsel assisting the commission, has spent the week questioning TWU officials about the McLean Forum, of which Mr Sheldon is a director.

Mr Sheldon challenged Prime Minister Tony Abbott and Employment Minister Eric Abetz to “come down to this court and explain why $52 million is being spent on this royal commission rather than setting up a national ICAC, a national inquiry into corruption in the political sphere, right across this country”.

He described matters addressed on Thursday by the commission as “trivial”.

During almost two hours in the witness box, Mr Sheldon repeatedly answered questions from Mr Stoljar around whether fund contributors knew how the money was spent.

He explained that contributors – union officials and employees – were well aware of how the fund would be used and expecting them to go back to every contributor could be compared to the Liberal Party going to every donor before they used the money donated.

The commission has heard that $200,000 from the McLean Forum was used to oust Queensland branch secretary Hughie Williams in 2010 and another $50,000 was used to back Gerard Hayes for the NSW Health Services Union’s top job.

Mr Sheldon said the commission should be congratulating him on that.

“Can anyone name a better chance to act in workers’ interests than the 2012 HSU elections, where yes, the McLean Forum donated to see the back of corrupt incumbents?” he asked.

Describing the forum as a political action committee, Mr Sheldon said Australia needed more of them to “stop the views of the anti-union uber-rich getting more and more clout at the expense of the ordinary working person”.

After giving evidence, Mr Sheldon told reporters he thanked the commission for giving him the opportunity to explain why the funds operate the way they do in a “political and corporate environment where the odds are stacked against working people”.

“This is a witch hunt by the government, set up as a witch hunt, when they should be investing their money in a national crime authority and releasing the 100 federal police to protect us against terrorism, to deal with pedophiles and to deal with the drug issues we have coming across our borders,” he said.

The commission resumes next week when it will revisit the Health Services Union.