Brushing aside yesterday's state election setback in Hesse, West Germany's opposition parties today reaffirmed their intention to topple Chancellor Helmut Schmidt in parliament Friday and install a new center-right government.

The final go-ahead for the plan is expected Tuesday. It hangs on a scheduled test vote among the 53 Free Democratic members of the lower house of parliament. They will be asked to indicate whether they support the effort to replace Schmidt with Christian Democratic Union leader Helmut Kohl.

Ten days ago the Free Democrats pulled out of the coalition with the Social Democratic Party that had ruled in Bonn since 1969.

Left-wing Free Democrats, pointing to the party's dismal performance in the Hesse election, renewed charges today that a Free Democratic shift to the right would cost the party its credibility and image as a progressive social force. In Hesse, the Free Democrats -- running on the pledge to form a new center-right coalition in the state as well -- failed to win the 5 percent of the vote required to stay in the state assembly.

"The Hesse results clearly do not back what we are doing in Bonn," declared former interior minister Gerhart Baum, a left-leaning Free Democrat, after a heated seven-hour meeting today of the party's presidium.

The election outcome, linked by analysts to public disapproval with the party's rapid alliance change in Bonn and to its bitter internal division over the move, added to speculation here that Free Democratic leader Hans-Dietrich Genscher will be unable to ensure his new conservative allies the votes they need to oust Schmidt.

Genscher had the support of 33 deputies when he broke with Schmidt 10 days ago. At least 23 Free Democrats are needed to complete the absolute majority required to remove Schmidt in a no-confidence motion, providing all 226 deputies of the Christian Democratic Union and the allied Christian Social Union also vote as expected against the chancellor.

"We will know tomorrow how many members of parliament from the Free Democratic Party caucus will give their vote to Dr. Kohl in the chancellor election," Genscher told reporters this afternoon.

Whether Genscher can garner sufficient backing for a new government depends heavily on the compromise program and appointments he concludes with Kohl and Bavarian Christian Social Union leader Franz-Josef Strauss. The three met tonight for six hours, and afterward Kohl said they had agreed on a policy program. He did not give any details, however.

Speaking of the plan to unseat Schmidt, Kohl told reporters this evening: "I will only agree to this kind of a vote if I can be sure that this vote will be successful."

Meanwhile, Strauss, known to be cool to the idea of a deal with the Free Democrats that would limit his own influence in a future coalition, gave little indication today of whether he intended to make things harder or easier for Genscher.

A top Strauss aide, Edmund Stoiber, said in Munich that the move against Schmidt depended on the Free Democrats demonstrating that they would be a clear and reliable partner in a new coalition. He said he was skeptical they could do this.

Stoiber, who is the Christian Social Union's general secretary, spoke of the Free Democratic Party as "at the moment not a calculable factor."

He said his party would like to see Genscher guarantee 40 votes in parliament Friday, but he added this was not a "firm condition."

"We will not be the cause if anything is wrecked," Stoiber said at least twice today.

In the Hesse vote, Schmidt's Social Democrats received 42.8 percent of the vote, while the Chistian Democrats won 45.6 percent, short of the absolute majority they had expected in the state. The Free Democrats received only 3.1 percent of the vote.

The vote, which showed a resurgence of support for Schmidt, was dismissed by conservative party officials as not representative of the country's general mood.

Kohl argued that the election had been tilted by the "dreadful emotional pressure" related to events in Bonn and the Social Democrats' bitter campaign against the new coalition negotiations. Stoiber said it was a deviation, not a change in the general trend.