I think this is one of those where the parodies are better-known than the original.

The version I've heard is:

"Ain't it a pity she's only one titty to feed the baby on
The poor little bugger will never play rugger or grow up big and strong"

The Two Ronnies (comedians Ronnie Barker and Ronnie Corbett) did a parody for one of their TV shows, which so far as I can recall went:

"Ain't it a pity the pubs in the city all close at half past ten
If I had the power they'd shut for an hour then open up again
I could get chronic on vodka and tonic at any time I like
And while the coppers watched my car I'd ride home on my bike"