Yeah yeah we've had this before. As far as I can tell your information comes only from one false study published in the USA and repeated in the media. If you've got any proper figures please PM me with them as I'd love to know. Personally I cant' see how one 30kg battery can take twice as much energy as the rest of the car to produce, which is what you're saying.
There are many studies out there, but most seem to be a few years old, which is useless both for the hybrid and the diesel. However, some things to ponder...
Ford Focus Diesel, 109 g CO2 / km
Newest Prius, 92 g CO2 / km
Whilst the headline figure is that the Prius is better on fuel, it will have cost considerably more energy to build, and almost certainly won't do 150k+ miles before popping its clogs. (A friend's - admittedly early - Prius needed new batteries after 60K). It also costs considerably more than the Focus. With which you could switch to a green energy supplier, fit solar thermal supplementary heating, or even (if you were determined to be green) get a turbine.
This Bluemotion Golf, 99 g CO2 / km is also cheaper than the Prius, has almost exactly the same tailpipe emissions, and again will do many more miles before it dies.
You should also bear in mind just how environmentally harmful that Ni in your battery is, and 30kg is a lot of it. It caused pollution being mined, caused pollution being transported and turned into said battery, and will cause pollution (or a lot of energy to be expended to minimise that pollution) when it needs disposal.
So no, Hybrids aren't that great really. Given a conventional car will probably run for twice as long, with marginally higher emissions, and save you some money to make some real emission saving elsewhere in your life too...