Parliamentary representatives of Zimbabwe-Rhodesia's white population today failed to support former prime minister Ian Smith's hard-line stance against British constitutional proposals for the breakaway colony.

After a 3 1/2-hour meeting in Salisbury, the parliamentary members of Smith's Rhodesian Front party said in a statement that "no good purpose would be served by taking up hard-and-fast attitudes at this delicate stage of negotiations and when the entire package deal is not yet known."

Abel Muzorewa, who replaced Smith as prime minister when the white minority surrendered domination of the colony's rule, has already accepted the British constitutional proposals.

The parliamentary group did give "unanimous" support to Smith's stance "in his determination to secure the best possible deal for minority groups in Zimbabwe-Rhodesia."

In a telephone interview, the chief whip of the white caucus in Salisbury, John Landau, characterized the statement as a "wait-and-see one" to see "what the final package produces."

If the party is not satisfied, however, he said it would oppose the final constitutional plan.

The tone of the statement is softer than Smith's fighting words in the Rhodesian capital yesterday when he told reporters that the proposals were the least attractive offered by the British government over the last 15 years in its attempt to bring the breakaway colony back to legal status.

Smith, who is now minister-at-large in the Muzorewa government, said that unless "significant" changes and a "number of improvements" were made in the constitutional plan it would be rejected by the Zimbabwe-Rhodesian Parliament, in which the 230,000 whites have a blocking veto.

But if Smith failed to get the unqualified support for his attitude toward the constitutional proposals, he may have succeeded in what some analysts see as another purpose in his return from the London talks at this time: to put political distance between himself and Bishop Muzorewa, who is battling the image of being Smith's puppet.

By returning to Salisbury now and publicizing his concerns with the constitution already accepted by Muzorewa, Smith distances himself from Muzorewa and in the process gives the bishop more credibility.

Smith, 60, was the only member of Muzorewa's 12-man delegation at the talks who rejected the British constitutional proposals.

Another reason for the white leader's apparent hard line against the constitutional plan no doubt is his desire to preserve his political image as the man who did not "sell out" the whites -- especially if the situation deteriorates under a British-sponsored settlement.

Even without the statement today, Smith's threat that the whites might block acceptance of the constitutional proposals, in effect overturning Muzorewa's acceptance of them last Friday, was regarded as a bluff.

The bishop needs only six white votes, in additiona to all 72 of the black legislators' votes, to alter the present constitution or replace it. He already has the support of Finance Minister David Smith, who voted with the bishop last week to accept the British proposals.

Muzorewa may also have the support of the two other whites acting as substitute delegates at the conference, Justice Minister Chris Andersen and Deputy Minister of Lands Rowen Cronje. According to well-informed sources both here in South Africa and in Salisbury, there are at least six and possibly a dozen whites in the caucus who would join Finance Minister Smith in accepting a settlement that the bishop signs.

The fact that the caucus left the door open and avoided repeating Smith's threat to reject the constitutional plan of the British suggests that the moderates within the parliamentary group argued convincingly today against taking a totally recalcitrant position.

The episode implies that Smith, who has always represented the most conservative of whites, may be losing his grip on a party he has led for 15 years now that whites must face the reality of playing a minority role in national politics.

In its statement today the Rhodesian Front said that "in the interests of maintaining confidence there must be provisions in the constitution which preserve law and order and ensure the security of the nation."

This is a code phrase for whites' desire to have a guaranteed continued role in the public service commissions that control appointments to top echelons of the police, judiciary and Army. Under the present constitution whites are in virtual control of these commissions.