A US Senator has called on the head of the US financial regulator to provide an update on the status of its reports into “apparently fraudulent comment letters” that showed support for proposed new rules on proxy advice.

In a letter addressed to Securities and Exchange Commission (SEC) Chairman Jay Clayton, Senator Chris Van Hollen asked about the progress of investigations into the matter, which took place more than six months ago, that the SEC had agreed to undertake.

The matter centres on a set of letters that were cited by Clayton as signalling support for proposed financial legislation that seemed set to restrict the activity and authority of proxy voting advisers.

These letters were purported to have been sent by “Main Street” investors, outlining their concerns around these advisers, but a Bloomberg investigation found they had been penned by an advocacy group with links to big business.

Following the discovery, Van Hollen grilled Clayton over the substance, validity and his belief in these letters, pointing out they were ultimately fakes and had been sourced from a “dark money group”.

“During the hearing, you did not specifically acknowledge that the letters, first reported by Bloomberg News, were in fact fraudulent,” said Van Hollen in this latest letter. “You stated that there was an investigation underway, that both the SEC’s General Counsel and Inspector General had been notified following the Bloomberg reports, and that you would wait to see what happened with the investigations.”

The Senator noted that more than six months later, no results from the investigation have been reported and urged him for an update.

“Please provide my office with any and all reports or findings of the General Counsel and the Inspector General, and whether there have been any referrals for criminal prosecution for the false representations made.”

He added that he would also like to know how the regulator intended “to account for the fact that the changes it is seeking in the regulation of proxy advisors do not appear to be based on concerns of ‘Main Street’ investors, as the revelations around the public comments clearly show, but instead emanate from corporate heads and boards that oppose investor oversight or review of their actions and proposals”.

Finally, he urged the SEC to hold off from finalising its proposed rule changes around proxy advisers until there was clarity around the letters. 

As of July 1, Clayton had issued no formal response.