Problem with running external process

[ToMasz]

There is a script running continuously which executes an external
script in a loop using os.spawnlp(os.P_WAIT, 'extscript.py') function.
After several hundred executions (cycles of the loop), the main script
gets an exception while trying to start the process. This situation is
repeated until the main script is killed. Before it is killed, no other
command can be executed - I'm getting the message:

-bash: fork: Resource temporarily unavailable.

How to properly execute another process from my script?