Ohio Secretary of State Ted W. Brown today certified petitions that will place on the Nov. 8 ballot an amendment to the state constitution that would cause repeal of Ohio's new "instant registration" law.

Brown said the group seeking the repeal - Ohioans for the Preservation of Honest Elections - had filed about 366,000 valid signatures nearly 60,000 more than required to qualify the amendment for the ballot.

Brown, a Republican and a leading opponent of the new voting law, predicted it would be repeated by "a substantial majority - at least 2 to 1."

However, Ohio Democratic leaders, who pushed the bill through the Democrat-controlled legislature, promised a strong counterrack to defeat the repeal.

Party chairman Paul Tipps said the anti-repeal campagin would cost $1 million, adding: We're confident we will have the resources to present our side of the story to the public."

Tipps said he would get help from the Democratic National Committee in hopes of developing a national campaign to preserve the new law's two main features: election-day registration at polling places and permanent registration.

President Carter has supported national "instant registration" legislation now before Congress on the grounds that it would encourage people to vote who now do not.%TThe Democratic Party in Ohio also expected substantial help from organized labor, the League of Women Voters, the NAACP and the National Urban League in an effort to sustain the law, enacted over Republican Gov. James A. Rhodes' veto earlier this year.

"We're taking this as a major party responsibility," Tipps said. "We want this to be a national referendum on the voting law."

However, supporters of repeal, who have insisted the new law would be vulnerable to massive voting fraud, say the ease with which they amassed the signatures within a few weeks is evidence of public disdain for the Democrats' action.

The repeal campaign was led by Jean Barren, president of the Ohio Association of Election Officials and a Republican member of the Jefferson County Board of Elections.