drop table in pgsql

Hi,

  How do I drop a table under plpgsql ?
  When  I  invoke a function which contains eg: DROP TABLE TMP a get a
  backend crash no matter if this table exists or not.

  I  can always do it the hard way and put DROP ... in an SQL function
  and then invoke DROP indirectly but do I have to ?

Please help me
Pawel Pierscionek