A trio of top Democrats from both chambers plan legislation aimed at rolling back a Supreme Court ruling they say makes it harder for plaintiffs to win age discrimination suits.

Tom Harkin , D-Iowa, chairman of the Senate Health, Education, Labor and Pensions Committee, and Patrick J. Leahy , D-Vt., chairman of the Senate Judiciary Committee, said Tuesday they will introduce a bill to restore a less-demanding burden of proof for plaintiffs in age discrimination suits. Rep. George Miller , D-Calif., chairman of the House Education and Labor Committee, said he intends to introduce a similar measure.

The proposed legislation is a response to the Supreme Court’s June 2009 ruling in Gross v. FBL Financial Services that plaintiffs claiming disparate treatment under the Age Discrimination in Employment Act must show that age was the determining factor in the alleged discrimination, rather than just one of several factors.

“The Gross decision established a far higher standard of proof for age than for other forms of discrimination, without any rationale or justification,” Harkin said. Leahy said the 5-4 decision written by Justice Clarence Thomas was evidence of an “activist Supreme Court.”

Under the proposed legislation, the burden would be on the employer to show it complied with the law once a plaintiff shows age discrimination was a “motivating factor” behind an employment decision.

The trio of lawmakers were joined at a press conference Tuesday by the plaintiff in the case, Jack Gross, who, at the age of 54, was transferred to a new position, which he alleged was a demotion. Gross is scheduled to testify at a Senate Judiciary Committee hearing on Wednesday.

This is the second time in a year that lawmakers have sought to counter a Supreme Court job discrimination decision.

In January, President Obama signed into law the Lilly Ledbetter Fair Pay Act making it easier for workers to challenge wage discrimination, responding to a restrictive 2007 Supreme Court ruling.