BONN, West Germany (AP) _ Chancellor Helmut Kohl on Monday blamed one of his party's worst state election losses in years on bickering within his coalition government and backlash from a political dirty tricks campaign.

Kohl's comments came after leaders of his conservative Christian Democratic party gathered to assess the damage done in Sunday's elections in the northern state of Schleswig-Holstein.

The chancellor's party was ousted from power in the state for the first time in 38 years, losing nearly 10 percent of the vote.

But the election was a decisive victory for the opposition Social Democrats, who won 54.8 percent of the vote after they had lost ground in a string of state elections over the past 18 months, according to the unofficial figures.

The results were the best-ever posted by the Social Democrats in Schleswig- Holstein, giving the party 46 of the 74 seats in the state's parliament, an increase of 10 seats from the previous election.

Unofficial results showed the Christian Democrats won 33.3 percent of the vote and 27 seats, down from 33 seats.

Sunday's vote was called to break the stalemate in the state's government that followed an inconclusive election in September 1987.

In that contest, the Christian Democrats polled 42.6 percent of the vote, while the Social Democrats got 45.2 percent.

''The clashes that occurred from time to time certainly did not help us,'' said Kohl, speaking of the in-fighting within his three-party federal coalition in Bonn.

The chancellor also told reporters that a principal cause of the unexpectedly large loss was ''the deep shock that lingered'' from the Barschel affair, one of the biggest domestic scandals to hit West Germany in recent years.

Uwe Barschel served as the Christian Democratic governor in Schleswig- Holstei n until he resigned last fall after news of a political dirty tricks campaign surfaced in the West German media.

Barschel was found dead in a Geneva hotel room in October, and authorities ruled his death an apparent suicide.

Meanwhile, the youth wing of Kohl's Christian Democrats called on the chancellor to reshuffle his Cabinet as a means of offsetting the Schleswig- Holstein election loss.

''A freshening-up of the coalition with younger people is urgently called for,'' Christoph Boehr, head of the Youth Union, was quoted by the Bild newspaper as saying.

After meeting with Christian Democratic leaders, Kohl acknowledged to reporters that his party had suffered a ''serious loss'' in the state elections.

But the chancellor said he was convinced the coalition would continue to be popular and predicted it would be re-elected in the 1990 federal elections.

Finance Minister Gerhard Stoltenberg, head of the Christian Democrats in Schleswig-Holstein, said at the same news conference that he had no intention of resigning his party position because of the election debacle.

The liberal Free Democratic party - the junior party in Kohl's governing coalition - also posted losses, falling from 5.2 percent of the vote in September to 4.4 percent Sunday.

The loss was decisive, because the Free Democrats failed to win the minimum 5 percent of the vote. Under West German law, a party must win at least 5 percent of the vote to take any parliamentary seats. As a result, the Free Democrats lost all four of their places in the parliament.

The environmental Greens party also failed to win parliamentary seats after receiving only 2.9 percent of the vote - well below the 3.9 percent it won in September.

It will be several days before the results, based on returns from polling stations, are verified and declared final under West German law.

Political analysts say the Social Democratic majority assures that the state governor's post will go to Bjoern Engholm, the party's candidate for the position.

The election turnout was 77.4 percent, up slightly from 76.6 percent last September.