THE LEGISLATIVE halls in Annapolis have been a sea of pinstripes all week as Maryland's bankers and their lobbyists scramble to recruit votes against allowing serious competition into their ranks. Consumers might well find much to like in some vigorous competition for the use of their money, but they're on the sidelines now as the state's bankers mobilize against an offer from Citicorp that would provide critical jobs as well as open up the banking market considerably. What the state's bankers seek is a more open market on their terms -- which means one that stays closed to certain competitors they either don't like or fear. Will the legislators succumb and kill an offer that Gov. Harry Hughes believes could help the state, particularly the depressed area of Hagerstown?

At issue are separate but related developments. Maryland's bankers, like most of their counterparts in neighboring jurisdictions, support the idea of interstate banking -- and it's a good one. Their desire for such a change led to a task force recommendation, and then a legislative proposal, to permit banks in 12 southeastern states and the District of Columbia to come into Maryland and do business. But -- and this is the key exclusion -- no other banks, including Citicorp, could come in for four years. This, Maryland bankers contend, would give the state banks time to "position themselves" for the arrival of the giants.

This prompted Citicorp to offer to open a 1,000- job credit-card service center near Hagerstown in exchange for the right to full banking privileges in the state by 1986. Gov. Hughes likes the idea; but the state bankers don't. They are now arguing, among other things, that the proposal comes too late in the session and would destroy their idea of a more limited -- exclusive is the word -- interstate system.

That's a flimsy excuse that some legislators may seize, but those who recognize the consumers' interest in this issue have a far better and more direct option: to agree on a reasonable and prompt date for allowing genuine, complete interstate banking -- and the competition for customers that comes with it.