Police Commissioner Andy Tsang Wai-hung, under fire for failing to make public in advance a visit to Beijing, said he had followed the force's practice in not disclosing the trip beforehand.
The government pledged last month to announce in advance working visits by secretaries and bureau chiefs, after Secretary for Education Eddie Ng Hak-kim was accused of keeping a visit to the capital secret.
Tsang arrived in Beijing for a three-day visit on Monday, but police only announced it late on Tuesday after a Chinese-language newspaper published a reader's photograph of Tsang flying to the capital.
After his return to Hong Kong last night, Tsang said he was not bound by the same rules as ministers such as Ng.
"We have different identities. [He is] a political appointee while I am a department head," he said.
"I am afraid you have misunderstood," he told reporters questioning him about his visit. "For all my official activities, I only make press releases after the activities have fruitful results. The practice this time is consistent with my previous practices."
However, the force last year announced a day in advance a visit by Tsang to Beijing.
Tsang said his visit, which involved a meeting with Wang Guangya , the director of the Hong Kong and Macau Affairs Office, and deputy minister of public security Chen Zhimin, was a courtesy call.
He said the pair had not discussed legislation for national security in Hong Kong or last week's voyage by activists to the disputed Diaoyu Islands.
Mak Yin-ting, chairwoman of the Hong Kong Journalists Association, criticised Tsang.
"He is appointed by the central government. How can he put himself on the same level as an ordinary department head like the director of water supplies?" she said.