An undercover surveillance company hired by the Commonwealth Bank has been caught secretly photographing senior politicians at a Coalition fundraiser.

The Sydney Morning Herald reported that the Commonwealth Bank hired security firm G4S to keep tabs on anti-banking lobbyist, Michael Fraser.

The surveillance operation took place between August 28 and September 1 when Mr Fraser was in Sydney for a private fundraising dinner for Nationals Senator John Williams.

In a memo obtained by The Sydney Morning Herald, the Commonwealth Bank requested photographs of people Mr Fraser met to ”allow for the identification of individuals”.

It said it was attempting to confirm if he was receiving information from bank insiders.

The Commonwealth Bank has defended its actions, saying Mr Fraser had launched “sustained and personal” campaign of “harassment, intimidation and threats” against one of its employees.

But Mr Fraser insists he has done nothing wrong, and maintains that his contact with the staff member has been appropriate.

“I think it’s interesting that they apply the word harassing to following up on an almost daily basis and trying to get something happening for the customers,” he said.

“I consistently hear about them ringing their customers sometimes up to 12 times a day and pressuring them to make payments or sell their house.

“Then they get upset about my approach, which is far less aggressive to the power of 10.”

Mr Williams says he has since accepted an apology from the bank.