nbsp removed during conversion to XHTML (tidy.exe)

During conversion of our command specs from HTML to XHTML ready for import
into an XML CMS (as legacy documents) we are using Tidy. Our thanks to all
who work here!

The problem is that our command specs rely heavily on   characters to
format the commands as follows:

<P>
<TT>
<A HREF="../../intrpt.htm" TARGET="_top">INTRODUCE_PART</A>(
<BR>
&#160;&#160;&#160;NAME=ABC001,
<BR>
&#160;&#160;&#160;OWNING_CATEGORY=CORESW1CT,
<BR>
&#160;&#160;&#160;DISC_SPACE=</TT><I><FONT
COLOR="#000099">disc-names</FONT></I>

<TT>
,
<BR>
&#160;&#160;&#160;DATA_SPACE=</TT><I><FONT COLOR="#000099">required-size
</FONT>
</I>
<TT>
)
</TT>
</P>

Where INTRODUCE_PARTITION is the command and the following lines are the
options.

Why does Tidy remove these spaces? I studied the XML and XHTML
specifications to see if &nbsp; and &#160; were deprecated in XHTML but
couldn't find anything.

Is it a bug or a feature? :-)

Thanks,
Richard