Tom Valentine, a professor at the Macquarie Graduate School of Management, has warned against a range of regulatory interventions in a submission to the Senate Economics Committee banking competition inquiry.Valentine's submission argues that critics of banks should look at the question of whether banks are earning above-normal profits. And it says the market return on bank shares of 13.8 per cent per year over the period 1981 to 2009 appeared reasonable, taking into account the possibility of greater risks in banking after the global financial crisis.The submission recommends an appropriate entity such as the Reserve Bank of Australia should release a regular report on bank returns. "If it is found that banks are extracting an excessive return, actions should take the form of increasing competition in the banking industry," it says.Valentine's submission argues there are reasons to be wary of several suggested regulatory interventions in banking, including:* measures to ease the act of switching banks;* encouragement for borrowers to take out fixed-rate mortgages;* regulation against price signalling; and * a post office bank.