Virginia Lt. Gov. Charles S. Robb, stung by criticism that he is too fuzzy on issues and too cozy with the state's Republican administration, today broke with Gov. John N. Dalton over a number of key issues facing the General Assembly.

Robb announced he would support repeal of state sales taxes on food, home heating oil and nonprescription drugs -- all of which are issues close to the hearts of many Democrats.

He faulted Dalton for opposing the Equal Rights Amendment, for not budgeting more state funds to meet Metro's operating costs and promised Democrats would closely scrutinize Dalton's gasoline tax increase proposal before deciding on approval.

Although Robb denied he was changing either his style or his political positions, other Democrats hailed his announcement as an indication Robb will play a larger role both as a politician and as the party's only statewide officeholder.

"I think it's super," said Del. Warren G. Stambaugh (D-Arlington), a sponsor of the food tax repeal bill and one of Robb's critics. "I think Chuck has realized that it's time we had a leader to stand up and say what we're for."

"He's taken stands before when asked," said Del. Alan A. Diamonstein (D-Newport News), one of a group of legislators who advise Robb. "This will just let more people know that he's a leader here."

A number of Democrats said Robb's new approach would enhance his chances of winning the governorship in 1981. Many party members have bemoaned Robb's lack of flair, saying it contrasted poorly with that of his likely 1981 GOP rival, Attorney General J. Marshall Coleman.

"Coleman likes to appear to be an instant expert on everything," said Del. Erwin (Shad) Solomon (D-Hot Springs). "Chuck's going to emerge as the more statesmanlike of the two."

Coleman refused comment on Robb's announcement, but his fellow Republicans said they believed the rejoicing of state Democratic leaders was premature.

"I'm not surprised Chuck's trying to do something," said GOP strategist William A. Royall Jr., one of Coleman's chief political advisers. "His candidacy is obviously in deep trouble in his own party."

Rovall cited as one sympton of Robb's problems the recent disclosure by retired Democratic Speaker of the House John Warren Cooke, that he is considering a bid for the party's nomination for governor. Robb said today he planned to meet with Cooke soon "to discuss matters of mutual interest."

Robb also said he would begin a series of weekly breakfasts with his party's legislative leaders to map out strategy and produce a program that can unite Virginia Democrats -- who hold a commanding majority of both legislative houses but are splintered by philosophical differences.

Robb's announcement marked the second time in two days that he has taken a more partisan role in legislative affairs. Presiding over the state senate yesterday, he ruled against a challenge by Republicans and two Northern Virginia Democrats who contended that the GOP unfairly had been excluded in key committee assignments.

In the past, Robb has said we would support the food tax repeal only if advocates could come up with a proved method of making up the lost revenues -- a position almost identical to that of Dalton.

Robb argued today that a study commission headed by Stambaugh adequately had demonstrated that phased six-year repeal would not significantly decrease state revenues.

Robb, a McLean lawyer, said his support of the food tax repeal stemmed from a belief that state government must address the needs of the poor and elderly who have been most hurt by inflation. We have to make some sort of effort to indicate to these people that we care about their problems," said Robb.

The GOP's Royall said he believed Virginians were most concerned with fiscal responsibility and that Robb's positions might gain him the Democratic nomination but lose the general election.

"Chuck's faced with the same old problem," said Royall. "To get the Democratic nomination, he has to say things that are 180 degrees different from what most Virginians want."