Like notorious New York criminal Willie Sutton, Scott Morrison is robbing the big banks because that's where the money is. The Treasurer needs the cash, including to pay for Labor's expensive spending monuments. The big banks have the cash, as AA-rated financial institutions that helped shield Australia from the global financial crisis should. And, as Mr Morrison, further explained yesterday, they don't have many political friends.

So a Liberal Treasurer whose economic growth strategy is based on cutting the uncompetitive 30 per cent tax rate for all companies, including big ones, slaps a new tax on some of Australia's biggest private financial institutions because it is politically convenient. Mr Morrison just as readily could have pickpocketed the gas industry, in a revamp of the petroleum resources rent tax which has been undergoing a formal review. At least that had some public process.

The new tax on certain bank liabilities – estimated to raise $6.2 billion over four years – has had none. Mr Morrison calls his bank stickup budget pragmatic and non-ideological. He could have said unprincipled, because he has undercut the core of his own jobs and growth agenda, or what is left of it, after the pivot to Labor's "fairness" agenda.

He has added to sovereign risk by endorsing the principle that any business impost is justified if it is politically popular. And he has poisoned the well for tax reform and added further complexity to the tax system, again made worse by Wayne Swan-like fiddles that try to camouflage the new levy's incidence. 'Nobody likes you anyway' was the Treasurer's disgraceful summary of the banks' position yesterday.

This fiddle includes carving out bank deposits up to $250,000 from the new bank liabilities' tax base, purely to try to show that this won't hurt any bank customers but rather will be somehow "absorbed" by the banks, given they have lots of money. But, if not passed on to customers, the billions of dollars of liability tax will have to come from bank shareholders, including millions of ordinary Australians. Or they could come from bank employees, given the government's correct arguments that taxes on capital are mostly ultimately borne by workers.

The tax grab comes on top of draconian new controls being placed on on bankers and banking business. Senior bankers – it's not clear how senior – will have to be registered with the Australian Prudential Regulation Authority, which will have powers to bar them from the industry, and to set their pay by clawing it back at a later date. APRA will approve senior appointments and board directors. So much for independent boards.

The regulator already lays down the law on banking areas such as lending and risk, and now it wants to handle personnel as well. Call it co-management, or bank socialisation. David Murray, who chaired the Financial System Inquiry, likens the new tax and regulation push to a throwback to the 1950s.

This has come about because of a populist race to the bottom between Labor and the Coalition in magnifying some non-systemic consumer banking misbehaviour into a systemic problem with our banks, putting them on the same footing as the 2008 basket cases of London and Wall Street, which demanded drastic reforms.

Our AA-rated banks helped stabilise Australia's economy during the GFC, but a Coalition government now finds them too useful as populist scapegoats. If big banks are to be cut down to size it should not be by treasurers but by marketplace competition. The "open banking" customer data regime also announced in Tuesday night's budget to might help do this, similar to portable phone numbers and super choice, and create new opportunities for fintech players.

At least this would be driven by the principle of competition, not by the political whims of a government that has failed to defeat the crass populism of its Labor opponent – so has instead decided to join it.