I want to create an environment which contains a list to typeset auto-numbered thesis (just like one does with math formulae). I would like the spacing to be something like this:

This is the code I've managed to create:
\newenvironment*{Tesis}
{\begin{list}
{\hspace{14pt}(T\arabic{tesisc})}
{\setlength{\rightmargin}{0cm}%
\refstepcounter{tesisc}%
\setlength{\leftmargin}{2\parindent}}
\item
}
{\end{list}}
which unfortunately renders thus:

I've fiddled with every list parameter I know of (\labelwidth etc.), but with no avail.
How can I tweak the list environment to accomplish the desired effect?
