Former Virginia lieutenant governor Henry Howell, longtime leader of the state's liberal Democrats, called on liberals yesterday to desert the party next year, a move that some party leaders day could hinder Lt. Gov. Charles S. Robb's chances of winning his expected race for governor.

Howell's comments yesterday, in which he criticized the party leaders for "taking stands on nothing and offending no one," bore a marked resemblence to statements he made in 1969 after losing a state runoff for the gubernatorial nomination. Party regulars say his admonition to liberals that year to vote as "free spirits" helped elect Republican Linwood Holton, the state's first Republican governor in this century.

It wasn't clear yesterday whether Howell's remarks will carry the same weight this time, but some of Robb's supporters were troubled nonetheless. "It's just a shame," said longtime Robb supporter Emilie Miller, former head of the Fairfax County Democratic Party. "We can't get anywhere if we keep fighting among ouselves as we usually do. I'm not saying we ought to agree one hundred percent, but we ought to at least get behind a candidate."

Howell's statement, which came in news interviews yesterday, culminated a long-simmering dispute between him and Robb, who is expected to be the party's gubernatorial candidate. Howell and other party liberals have frequently accused Robb of being too conservative and refusing to take stands on major state issues, charges which Robb has rejected.

Robb, however, is known to be concerned about the liberal image the party projected while Howell was active in it, and has sought to project a much more conservative image.

Howell, a fiery populist leader who has lost three races for governor, said his split from the party's increasingly conservative leadership began with the defeat of two of his allies by conservatives seeking seats on the Democratic National Committee last May. The last straw came with the defeat two weeks ago of H.R. (peck) Humphreys of Kilmarnock in the contest for state party chairman. Humphreys was downed by Del. Owen B. Pickett of Virginia Beach, who had been supported by Robb.

"It was clear that liberals aren't wanted by the rest of the party," Howell said yesterday. "They had real people who had worked for the party for years . . . and they went out of their way to dump them because they felt they would be harmful in electing a Democratic governor."

Howell said he would play no role in the 1981 gubernatorial election, and did not plan on lending an advance endorcement to Robb, who has been careful to disassociate himself from the liberal wing of the party. Robb, who lives in McLean, could not be reached for comment yesterday.

"I'ves got something else to do [next year] and I think I can do something more meaningful when the politics of Virginia have returned to the politics of the past and the best way to get elected is to take a stand on nothing and offend no one," said Howell in an obvious swipe at Robb. "This is not sour grapes, but I'm not interested in sipping tea or dancing the minuet."

Howell's statement appeared to be exactly what Robb supporters have feared for some time. While many party leaders question Howell's appeal to the state's electorate today, they say he still can command the loyalties of many party activists whose support is crucial to any Democratic candidate.

"[Howell] could very well decide the election for governor or for any other statewide contest," said Howell ally Humphreys. "It's the swing vote that's been determining statewide contests for the past few years, and that's how the Republicans have been winning."

"This is the best possible thing that could happen to Chuck [Robb]," said former state attorney general Andrew P. Miller of Alexandria, a longtime Robb supporter. "For the last decade, the Republicans have been running against Henry Howell. Now they don't have him to run against anymore."