WASHINGTON - A dozen more banks are protesting the government's plan  to capitalize the Savings Association Insurance Fund through a one-time fee   on thrift deposits.   
In a letter last week to Federal Deposit Insurance Corp. Chairman Ricki  Helfer, 12 banks argued that they should not be penalized for having bought   thrift deposits.   
  
"At no time were we informed, nor did we contemplate, that, by  purchasing thrift deposits, commercial banks would be subject to a special   assessment," wrote the banks, which are being represented by Diane Casey,   director of financial institutions regulatory issues for Grant Thornton   here.       
The government's proposal, delivered to Congress in July, would build  the thrift fund by raising more than $6 billion through an 85-basis-point   fee on all thrift deposits held by financial institutions as of March 31.   
  
More than 700 banks that have bought thrift deposits would owe about  $1.6 billion, according to Randy Dennis, president of DD&F Consulting Group   in Little Rock, Ark.   
Mr. Dennis said including bank holding companies that own thrifts would  add $536 million, bringing the banking industry's share of the $6 billion   total to $2.1 billion.   
Last week's letter was preceded by a letter from 11 other banks Aug. 7  complaining to Ms. Helfer that they are being asked to pay a fee on   deposits that no longer exist.   
  
These bank companies, including Banc One Corp. and Barnett Banks Inc.,  argued that it is unfair to levy an assessment on thrift deposits when up   to 40% have run off.   
The FDIC is studying the letters, but Congress is expected to consider  the issue after Labor Day as part of the administration's rescue plan for   the thrift fund.   
The letter last week urged the FDIC to discount the fee for banks that  bought thrift deposits recently. 
"Failing to reflect the length of ownership of the deposits distorts the  economics of these Oakar transactions," the letter said. "An adjustment   should be made to account for the economic impact on commercial banks that   have not owned their SAIF-insured deposits long enough to recover their   investments."       
  
The banks, including Compass Bancshares Inc., Birmingham, Ala., proposed  10% reductions for each year deposits were owned after 1990. A bank that   bought thrift deposits in 1990 would pay the full 85-cent assessment per   $100 of all its thrift deposits. But a bank that bought thrift deposits in   1994 would only have to pay on 60% of its deposits.       
For example, Prime Bank in Channelview, Tex., which bought $400 million  of thrift deposits in October 1994, would pay roughly $2.1 million under   the proposal instead of $3.4 million.