A divided panel of Connecticut regulators on Wednesday gave final approval to Iberdrola USA’s $3 billion takeover of UIL Holdings.

The state’s Public Utilities Regulatory Authority voted 2-1 in favor of the deal, which it had tentatively approved last month. (See Connecticut Regulators Poised to OK Iberdrola Acquisition of UIL.)

In a dissenting opinion, authority member Michael Caron said the deal presents “too many unknowns” for regulators and the state’s ratepayers.

“Iberdrola is a multi-national conglomerate that is currently engaged in regulated and unregulated activities,” he wrote. “Consequently, parts of Iberdrola’s business may be more inherently risky than its regulated utilities. These risks outweigh the minimal public benefits provided in the settlement agreement.”

Iberdrola agreed to regulators’ demand for “ring fencing” of the company’s state operations from its other domestic and international holdings. But Caron said that the company’s responsibilities to its shareholders overall would undermine those protections for Connecticut ratepayers.

Caron also said Iberdrola’s previous ownership and sale of two Connecticut natural gas distribution companies showed a lack of commitment to the state.

In a statement, PURA Chairman Arthur H. House said the deal was in the public interest and overcame objections that officials had to the first proposal last summer.

“While their first proposal had many positive aspects, Iberdrola and UIL took to heart the message we sent in our preliminary ruling, measurably improving both the public benefit content of their proposal, and also making specific, measurable commitments that ensure the flow of benefits to utility ratepayers,” he wrote.

PURA Vice Chairman John Betkoski joined House in approving the acquisition.

The deal had won the endorsement of the state’s Consumer Counsel in September.

The deal must still be approved by UIL shareholders and Massachusetts regulators, who have jurisdiction over UIL’s natural gas distributor Berkshire Gas. The companies have asked that state’s Department of Public Utilities to rule by Dec. 18.