MOTORISTS may pay less to park after a government decision to appoint a second operator to run its car parks from next month. Wilson Parking will hand over half of its management contracts to the Wharf group, ending nine years of monopoly, the Transport Department announced yesterday. A Wharf subsidiary, Metro Park, has been granted a competing franchise to run seven government car parks until May 1, 1997. The 4,039 parking spaces - at Star Ferry, City Hall and Murray Road in Central, Middle Road in Tsim Sha Tsui, Aberdeen, Kwai Fong, and Tsuen Wan - are estimated to yield an annual revenue of about $150 million. Wilson Parking will continue to run 4,135 spaces at the remaining seven car parks at Garden Road and Rumsey Street in Central, Tin Hau, Shau Kei Wan, Yau Ma Tei, Tze Wan Shan, and Tsuen Wan until May 1997. The Government monitors parking fees and pays the operator a percentage of revenue. But government controls would prevent Wilson from offering parking discounts or launching a price war against Metro, said Wilson managing director Mr Paul Simpson. He said he was happy with the tendering result because the company had been given a fair share of government contracts. The loss in revenue would be more than compensated for by expansion in the private sector, he said. Wilson Parking operates about 40,000 spaces in the public and private sectors. But Mr Simpson was worried that the end to his company's monopoly might mean inconvenience to some motorists. ''It would be unfortunate for some drivers if they can no longer use one parking pass at all the five car parks in Central, for example,'' he said. Wharf Holdings managing director Mr Gerry Higginson said improvements in services would be necessary to make profits. Motorist Mr Francis Cheung, who holds a Wilson quarterly parking pass, said he hoped parking fees would drop and management would improve with the end to the monopoly. He said his pass did not guarantee a parking space. ''Even though I have a ticket, I have to queue up at the car park if it's full. I think that should be improved,'' he said last night at the Tin Hau park. Wilson's charges vary according to the location. The fee for a 30-minute slot at Tin Hau is $6 between 7 am and 11 pm and $4 at other times, while prices at the Star Ferry are $7.5 and $5.