Warren Buffett, who has long slammed the hedge fund industry for charging high fees, escalated his criticism of private-equity firms that have been raising record sums of money in recent years.

“We have seen a number of proposals from private equity funds where the returns are really not calculated in a manner that I would regard as honest,” Buffett said Saturday at Berkshire Hathaway Inc.’s annual meeting. “If I were running a pension fund, I would be very careful about what was being offered to me.”

Buffett has a consistent history of blasting asset managers for charging high management fees and collecting performance fees on gains that sometimes don’t beat broader markets. The presence of private-equity firms looking for leveraged buyouts of companies has also made it tougher in recent years for Buffett to find large acquisitions for Berkshire.

“We’re not going to leverage up Berkshire,” Buffett said.

Buffett and Berkshire Vice Chairman Charles Munger criticized how some private equity firms portray performance. Firms will include money that’s sitting in Treasury bills waiting to be deployed when charging management fees, but will exclude it when calculating a so-called internal rate of return, the performance measure in which most funds are judged, Buffett said.

“It makes their return look better if you sit there a long time in Treasury bills,” Buffett said. “It’s not as good as it looks.”

Munger described the practice as “lying a little bit to make the money come in.” He added that many pensions are picking private equity because they don’t have to mark down the value of the assets as steeply in a downturn, saying that this was “a silly reason to buy something.”

Buffett has previously criticized the use of debt by private equity funds, saying in his 2014 letter to shareholders that Berkshire offers another, more permanent buyer, when people are looking to sell their businesses. He acknowledged on Saturday that leveraged investments would outperform in good environments, but he cited the 1998 collapse of hedge fund Long-Term Capital Management as an example of the downside.

While some have argued that Berkshire has embedded leverage by being able to use cash flows from its insurance businesses in acquisitions, Buffett said he wouldn’t be adding debt to chase deals.

“Covenants to protect debt holders have really deteriorated,” Buffett said. “I would not get excited about so-called alternative investments.”