U.S. lawmakers plan to look into the relationship between bankrupt mid-size brokerage firm MF Global Holdings Ltd's former CEO Jon Corzine and the major credit-rating agencies, The Wall Street Journal reported on Thursday, citing a person familiar with the matter.

MF Global's credit ratings were cut to junk in the days before its October 31 bankruptcy.

A U.S. congressional subcommittee plans a December 15 hearing with regulators and top MF Global officials to review the firm's collapse. The House Financial Services Subcommittee for Oversight and Investigations has invited Corzine and Bradley Abelow, the firm's chief operating officer.

The Journal, citing its source, said the committee's members plan to look into the interactions between Corzine and rating agencies like Moody's Investors Service, Standard & Poor's and Fitch Ratings and whether their judgment was clouded by the prominence of the former New Jersey governor and one-time head of Goldman Sachs.

Lawmakers haven't yet asked any firm to attend the hearing, the Journal's source said.

Representatives for Moody's, S&P, Fitch and MF Global did not immediately respond to requests for comment.

A representative for Corzine could not immediately be reached.

(Reporting by Phil Wahba; Editing by Jan Paschal)