LONDON -- Singling out good stocks is quite an art, but what about bad stocks? For the last few months, I have been working through the FTSE 100 (UKX), looking for great opportunities. Along the way, I have found plenty to avoid. Are these the worst five stocks on the FTSE 100? And if so, how come I own three of them?

Royal Bank of Scotland
Like most people in the U.K., I loathe Royal Bank of Scotland (NWG 1.04%). Its arrogance cost taxpayers hundreds of millions. It's a bad bank, propped up by the state, which owns 85% of it. One day, that stake will have to be offloaded, which could wreak further damage on its share price. Like all banks, it still attracts scandals like jam attracts wasps. RBS has also been accused of abandoning U.K. PLC by failing to lend during the downturn. Worst of all, like most big banks, its vast, sprawling balance sheet is impossible for ordinary mortals to understand. RBS is so bad it is almost good, which is why I bought its shares a couple of years ago at 21 pence. They now trade at 35 pence, a rise of 67%. Do I hate RBS, or do I hate myself even more for speculating on it?

GlaxoSmithKline
Here's another stock I hate myself for holding: pharmaceutical giant GlaxoSmithKline (GSK -0.92%). Unlike RBS, this one has hardly made me any money since I bought it five years ago. What I find astonishing is that it still has such a healthy reputation with investors. It is more likely to figure in the best five FTSE 100 stocks, rather than the worst. That annoys me as well. So does the fact that it recently extended the amount of time it takes to pay suppliers from 60 days to 90 days, a sneaky move that has drawn anger from small businesses. Most annoying of all, its share price is down nearly 10% since last summer. So much for defensive pharmaceutical stocks. Crikey, even AstraZeneca has done better lately. Glaxo has also seen drugs sales fall in austerity-stricken Europe, and I worry that more bad news could follow. On the plus side, there is that 5.1% yield. There may be far worse stocks on the FTSE 100, but few are quite as frustrating.

ICAP
Wholesale broking business ICAP (LSE: IAP) has found it tough since the financial crisis, thanks to a slump in derivatives trading. After a series of profit downgrades, it is trading at roughly half its peak value five years ago, and the slide continues. It has fallen more than 40% in the last 12 months alone. Chief executive Michael Spencer has called this one of the toughest periods of his career, and you can see why. It is always darkest before the dawn, however, and some of you might consider this a contrarian buy. Broker Prime Markets recently called ICAP "a recovery to buy into." If you agree, this stock's 6.8% yield will reward you for your patience, but you may have to be very patient indeed.

BG Group
What can you say about a stock that has just admitted it won't grow this year, and probably won't do much better next year as well? The stock market knew exactly how to respond, which is why BG Group's (LSE: BG) share price plunged 20% last year. I treated this as a buying opportunity, but I'm beginning to suffer buyer's regret, as the share price has little reason to go anywhere right now. There has been a spark of good news this year, with production starting on time and on budget at the group's Sapinhoa offshore field in Brazil. There has even been some takeover speculation, with rumours of a bid from Royal Dutch Shell and Petrobras. Again, buyers will have to be patient, only this time they will receive scant reward from the dividend, which yields just 1.4%. BG Group owes its investors better than that.

Admiral Group
When I last looked at Admiral Group (ADM -1.12%), the thing I like most was its subsidiary brand Confused.com, one of the best-established price comparison sites in the U.K. But the group is sailing through choppy waters right now. Its most recent trading update saw a 2% drop in quarterly turnover to 570 million pounds, year over year, as premium rates fell in the cyclical car insurance market. This is a highly competitive market, and Admiral may struggle to replicate its stellar growth of the last 20 years. It is a financially solid business, so there is little reason for investors to worry, but little reason to get excited either. Especially on a dividend yield of 3.2%, that can be bettered elsewhere.

Great eight
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