Lobbyists on both sides of the issue of establishing a new consumer agency were pressing hard yesterday, expecting that after eight years the issue will finally be decided by the House in the next couple of days.

The White House is strongly backing the bill. Yesterday President Carter told his cabinet secretaries to get actively involved in lobbying for the agency. Carter himself is making phone calls to House members, press secretary Jody Powell said. House debate will begin today and a vote is expected either today or Wednesday.

"It's a very close, very tough fight. It will be close either way," Powell predicted.

"We have a very good chance of winning it," House Speaker Thomas P. (Tip) O'Neill said. He called it "definitely one of our issues. I do hope we pass it," he said.

Republicans and business groups opposed to the bill are also confident that they have the votes to beat it. "I don't see how the Democratic leadership can think it has the votes to pass this bill," one Republican member said. He predicted that only about 15 Republicans would support the measure.

The bill was taken off the House calendar last November, when the Democratic leadership decided there were not enough votes to pass it, even thouh it had been considerably scaled down from earlier versions.

Originally the legislation would have set up a consumer protection agency, with broad powers to intervene on behalf of consumers before regulatory agencies and other government departments.

In its latest version, the bill would establish an Office of Consumer Representation, with more limited power to intervene on the consumers' behalf. The office could not demand that businessmen answer questionnaires, and would not have special standing in appealing federal agency decisions in which it had not participated.

In addition, the functions of 20 consumer representatives already set up in a number of executive departments would be consolidated in the new office, for what proponents say would be a saving of $6.6 million.