Fitch Ratings downgraded the viability rating of Hongkong & Shanghai Banking Corp. Ltd. to "a+" from "aa-."

The rating agency said Dec. 5 that it affirmed the bank's short-term issuer default rating at F1+, while its long-term issuer default rating of AA- remains on Rating Watch Negative.

The downgrade is in line with the downgrade at its parent HSBC Holdings PLC, Fitch said. It added that the Hong Kong unit's viability rating reflects its intrinsic strength, which is in turn underpinned by support from the parent company through the group's integrated business model.

Fitch believes challenges to HSBC's business model will affect Hongkong & Shanghai Banking Corp. due to the high levels of integration and connectivity within the group, which ultimately derives its overall strengths from its international network.

The Rating Watch Negative on Hongkong & Shanghai Banking Corp.'s long-term issuer default rating mirrors the Rating Watch Negative on its parent company and reflects the heightened risk that Fitch may assign a negative outlook on the banks in the event of a no-deal Brexit.