UPDATE : Labour's Lord Myners, who really ought to know better, is now (Thick of It style) pushing a rival plan this morning. Forcing investment banks to reduce their fees for capital raising. He seems to want to further erode bank profits. How are the banks expected to rebuild their balance sheets?Does Guido actually understand how investment banking works? Investment banks shouldn't need to rebuild their balance sheets because they don't provide the money themselves, they act as facilitators matching those with cash to those who want it and take fat fees for this job.
Now, it's true that in these times the traditional "investment bank as an agency" model is a rarity with most banks being a larger banking conglomerate. However, it should be still be noted that the purpose of the investment bank is to find capital to fund it's customers, if it is charging excessive fees in order to shore up it's parent bank's balance sheet that smacks of an absolutely massive conflict of interest.
From what we can read into Guido's post, it seems clear that he either does not understand what in investment banking is or he is not worried about this conflict of interest. If it's the latter then he's being little more than a political lobbyist demanding that that the banking gravy train continues unabashed.