WELLINGTON (Reuters) - Spark New Zealand (>> Spark New Zealand Ltd) said on Tuesday it was formally opposing a merger between Sky Network Television Ltd (>> SKY Network Television Limited) and Vodafone Plc's (>> Vodafone Group plc) New Zealand unit, stating that Sky's monopoly on premium sports content rights in New Zealand is a key concern.

"Based on Sky’s current wholesale market arrangements for premium sports content, we don’t believe the proposed merger is in the best interests of New Zealand consumers and so should not go ahead in its current form," said Spark New Zealand's general manager regulation, John Wesley-Smith.

Pay TV provider Sky Network and Vodafone in June announced a proposed deal under which Sky Network will buy New Zealand's No. 1 mobile phone provider for NZ$1.3 billion (728.19 million pounds) in cash, to be funded through new debt, and the rest in new Sky shares. Vodafone will own 51 percent of the combined entity if the deal goes through.

The transaction remains subject to regulatory approvals from New Zealand's Overseas Investment Office and the Commerce Commission.

"A merged Sky/Vodafone will be able to leverage its monopoly power in the sports market, to the detriment of consumers. That's why we’re asking the Commerce Commission to reject the proposed merger in its current form," said Wesley-Smith.

(Reporting by Rebecca Howard; Editing by Matthew Lewis)