Many of the world’s largest private equity firms face an investigation into strategies that may have helped them to avoid paying hundreds of millions of dollars in US taxes.

The groups being investigated by New York’s attorney-general, Eric Schneiderman, a Democrat, include Bain Capital – formerly led by Barack Obama’s Republican presidential challenger, Mitt Romney – KKR and Apollo Group, a person familiar with the investigation said.

“This is shamelessly political, but it’s to be expected and I’m surprised it hasn’t happened sooner,” said one private equity executive. “You have a right to privacy, but you don’t have a right to be president. If Bain and Mr Romney saved themselves tens of millions of dollars in taxes, then you would expect that to be examined.”