The Massachusetts House of Representatives last night put its final stamp of approval on the Gay Rights Bill, clearing its last major obstacle on the path to becoming law.

The House, which approved the original draft of the bill last summer, voted by a slim margin to accept an amended Senate version of the bill, 79-73, after more than two hours of often-heated debate on the House floor.

The bill now requires a final senate enactment vote and the governor's signature. Supporters said they expect little difficulty in getting the Senate to approve its own amended bill, and Gov. Michael S. Dukakis has promised to sign it.

"This was it. This was the last hurdle," said David LaFontaine, lobbying director for the Coalition for Lesbian and Gay Civil Rights. "Today was [the opposition's] last chance, and we decisively defeated them."

"We knew we had the votes to win, but the question was `will everyone stay?'" said Arline Isaacson, co-chair of the Massachusetts Gay and Lesbian Caucus.

The bill, which bans discrimination in housing, employment and credit on the basis of sexual orientation, has been defeated on Beacon Hill for the last 17 years.

The majority in both houses supported the bill last year, but opponents held it in a Senate committee until the bill died at the end of the legislative session.

After agreeing to consider the amended bill last night, representatives engaged in what they called an "unpleasant" debate on the House floor.

"It's a phony piece of legislation," Rep. William J. Flynn Jr. (D-Hanover) told the House. "We're talking about an imagined wrong."

"Where hatred exists, discrimination exists," Rep. Mark Roosevelt '74 (D-Boston), the bill's chief sponsor in the House, said in response. "Discrimination exists in Massachusetts. It exists in this building."

The three amendments tacked on to this year's bill by the Senate grant religious exemptions, ban gay marriages and state that the Commonwealth does not endorse homosexuality.

Supporters of the bill said the amendments have no legal teeth, but are written in "offensive language."

Legislators and gay rights lobbyists decided to accept the altered version instead of trying to remove the amendments in a conference committee, where opponents would have a chance to stall the bill's passage.

The Senate is expected to hold the final vote on the bill sometime this week.

"It has been absolutely grueling," Isaacson said of the legislative battle. "Every year we were defeated, we came back, and the message that was sent to the legislators was `we'll be back again and again and again.'"