Greens MP Adam Bandt said his party's banking bill, currently before the House of Representatives, was "just the start" of a number of changes the party hopes to make to the financial services industry.The Greens see merit in imposing a levy of around 20 basis points on the big banks, in recognition of the benefit they receive from operating in a "government fostered" oligopoly.They want to see the introduction of account portability, so customers can move their transaction accounts as easily as they move their mobile phone accounts.The party is also investigating the merit of imposing a levy on private ATM operators and using the funds to put ATMs into remote areas.And it would like to see changes to the Consumer and Competition Act so the Big Four banks are prevented from acquiring any more second-tier institutions.Speaking at an Australian Bankers' Association conference in Sydney yesterday, Bandt said the philosophy underpinning all these ideas was that banking was an essential service that should be free.Bandt, the Member for Melbourne, is the first Green to be elected to the House of Representatives. In July, when new Greens members enter the Senate, the party will have the balance of power in the upper house.Bandt has already introduced the Banking Amendment (Delivering Essential Financial Services) Bill, which proposes the banning of mortgage exit fees (already taken up by the Government). It also includes a cap on foreign ATM transaction fees, a requirement that all banks provide a fee-free transaction account, and a requirement that lenders offer "tracker mortgages", which move in line with changes in the official cash rate.Bandt said: "The reality is that true competition does not exist in Australia. Successive governments have fostered the oligopoly position of the big banks."There have been some adjustments from time to time, such as allowing increased participation of foreign banks, but, overall, there has been a reluctance to really allow anything to challenge the position of the Big Four."These policies stem from the desire of successive governments to maintain a strong banking sector with a low risk of failure. They correctly see many banking services as essential services and believe that a strong banking sector underpins a strong economy."Isn't it time the beneficiaries of this policy should be asked to provide something in return?"His idea for a 20 basis point levy on the big banks comes from the International Monetary Fund, which reported that the guarantees to the financial sectors of developed countries were worth around 20 basis points.