The first major submission to the Senate's banking competition inquiry argues for limits on lenders' ability to change loan interest rates and exit fees, and for greater freedom for borrowers to transfer loans.The submission, from the Australian Centre for Financial Studies, was prepared by the centre's research director, Kevin Davis. It focuses on the mortgage contract, reasoning that the US sub-prime crisis has shown that badly designed mortgage contracts can create social and economic problems. Its key points:* Australian housing mortgage rates should not be variable at the lender's discretion. Home borrowers are unlikely to be able to anticipate the effects of future market disruptions, and it is more appropriate that those risks be borne by bank shareholders and managed by bank executives. "Adjustable rate loans where the rate is specified as a fixed margin over a variable market indicator rate for some period ... are one option," the submission says.* At re-negotiation dates, borrowers should be able to transfer a mortgage to another lender at minimum cost, as is the case in Canada.* Lenders should be banned from charging exit fees on housing loans at re-negotiation dates, once the loan is three years old.* Lenders should only be able to charge deferred loan establishment fees by explicitly adding them into the initial loan principal.Other submissions to the Senate inquiry so far, from members of the public, call for changes that include a new government-owned retail bank to  "some sort of common bank fees for all different accounts across the country [so] regulating different banks charging whatever they like to cover their expenses and still earn billions ... [in] profits."