Fitch Ratings has affirmed the ratings of New Zealand's four major banks: ANZ Bank New Zealand, ASB Bank, Bank of New Zealand and Westpac New Zealand. The Outlook on their respective long-term issuer default ratings remains 'stable'.This affirmation of the major banks' LDRs as 'stable' reflects Fitch's view that there is "an extremely high likelihood of support from their parent banks, should it be required." The rating agency said it views the NZ banks as "core subsidiaries" of their respective Australian parents, "given their focus on core customers and products which align with their parents' strategies.""The strong likelihood of support is reinforced by the regulatory linkages between Australia's and New Zealand's authorities," Fitch noted in a media release. "We expect both authorities to work closely to ensure the stability of each other's financial systems." And against a weakening of the dairy sector, the ratings agency's view is that other parts of the economy appear well covered: risks in mortgage books appear adequately managed, particularly as interest rates remain below historical averages and price inflation accelerated in 2015.Further, the recent reduction in higher-LVR mortgages should mitigate the potential risk to banks' asset quality in the event of a substantial downturn in property values following a sharp increase in house prices during 2015 - particularly in Auckland. Fitch said it expects the majors to maintain their improved funding and liquidity positions. "A continued focus on longer-term wholesale funding and improving the quality of deposits is likely in 2016. The banks should remain reliant on offshore wholesale funding markets in the medium term, reflecting a general lack of deposits in the New Zealand market," Fitch said.