Pressure is mounting on Attorney General Cuomo to launch an investigation into the New York City Board of Elections and its undercounting of Senator Obama’s share of the February 5 presidential primary vote in the city’s voting districts, following sharp criticism by Mayor Bloomberg yesterday.

“This is just an outrage,” Mr. Bloomberg said. He called the Board of Elections “the last openly, outright, pure, partisan patronage organization we have in this state and in this city.”

The Board of Elections confirmed newspaper reports this week that about 80 election districts reported unofficial vote counts in which Mr. Obama received no votes in the primary. Revised counts showed that he earned significantly more votes, possibly affecting his allocation of delegates.

“What they do is hire on the basis of politics, and obviously the people that they have aren’t as competent as you would like, because the results that they reported just defies credibility,” the mayor said. “The probability of Obama in some of those districts getting zero votes is zero. Let’s get serious here.”

In a letter to Governor Spitzer yesterday, the executive director of an advocacy group, Citizens Union, Richard Dadey, urged the governor and Mr. Cuomo to launch an investigation into the circumstances of the primary day errors and take “whatever steps necessary” to reassure voters that elections are fair and the results are reported accurately.

A spokeswoman for the city’s Board of Elections, Valerie Vazquez, said the scale and nature of the voting errors, which she attributed to human error, had been overstated.

“We’re disputing unofficial results, and they’re just that — unofficial. I don’t know how much more of a disclaimer we can put up there,” Ms. Vazquez said. “There are sometimes discrepancies, but we’re talking 6,106 election districts within the city of New York, and there are 78 of them in question.”

The official vote is expected to be certified on February 26.