Influential financial services research firm Forrester has called on National Australia Bank and Commonwealth Bank to offload their mortgage broking and aggregation services arms as part of their wider efforts to rebuild trust with customers.In a report published on Tuesday, senior Forrester analyst Zhi-Ying Barry argues that the banks should sell their third-party mortgage distribution platforms to resolve the "inherent conflicts of interest" identified by the Hayne Royal Commission."The Royal Commission found that brokerages affiliated with big banks tend to direct loans to their parent company," Barry states in the report."While there's talk about decoupling mortgage brokerages from banks, so far nothing has been done."Banks should sell or restructure their mortgage broking businesses in order toappear fair and honest and to rebuild trust with customers by showing them that the bank has their best interests at heart."In the last year, CBA has tried to offload its troubled mortgage broking subsidiary, Aussie Home Loans, but last month suspended the sale process. By contrast, National Australia Bank has never flagged any plans to sell its three mortgage aggregation platforms - Fast, Choice and Plan - that together give the bank special access to around 4000 mortgage brokers across the country. While most other major banks have struggled to grow market share in home lending in the last 12 months, the proprietary broking channel has helped NAB to expand mortgage volumes consistently.Barry warns that Australian banks will need to dedicate more resources to developing direct-to-consumer offerings as governments and regulators move to ban trail commissions and cap upfront payments to brokers."Currently, the broker channel represents a significant source of mortgages for big banks," argues Barry."The prospect of lower commissions will fuel the exit of a growing number of brokers."Leading firms will elevate direct-to-consumer digital capabilities - they'll focus not only on transparency and simplicity, but also on building relationships and supporting customers, especially first-time home buyers, with human assistance - which is why customers go to brokers in the first place."While Barry contends that the Australian government should prohibit the practice of allowing lenders to pay commissions to brokers, neither of the major political parties has accepted this recommendation from Hayne.The Morrison Government announced last month that it was committed to retaining trail commissions for at least the next three years and the Labor Opposition is developing a compromise policy that would allow lenders to pay a capped upfront commission to brokers.With industry groups such as the Mortgage and Finance Association of Australia continuing to rail against the Hayne recommendations, shadow treasurer Chris Bowen is likely to come under pressure during the election campaign to give more detail on how a Labor government plans to rework broker remuneration.Bowen has not commented publicly on whether a Labor government would require banks to divest third party distribution channels such as NAB's Choice and Plan subsidiaries.