LONDON -- Management can make all the difference to a company's success, and thus its share price.

The best companies are those run by talented and experienced leaders with strong vested interests in the success of the business, held in check by a board with sound financial and business acumen. Some of the worst firms are those run by executives collecting fat rewards as the underlying business goes to pot.

In recent weeks, I've been assessing the boardrooms of companies within the FTSE 100. Today I'm naming and shaming the bottom five companies from the 60 companies that I have looked at so far.

I look at management teams from five different angles, giving each a mark out of five. The scores are added to produce an overall score out of a maximum 25. These are the bottom five:

 ReputationPerfor-manceCompositionRemun-erationShare-holdingsOverall
Score
Marks and Spencer 3 2 3 1 2 11
Aviva 4 2 2 2 1 11
Barclays 3 2 1 1 4 11
RBS 3 2 3 2 0 10
International Consolidated Airlines 4 3 0 2 1 10

It's a measure of how fast-moving things can be that some of these boards would get higher scores now than when I originally analysed them. In particular, things have changed at RBS (NWG 1.36%)Barclays (BARC 6.73%) and Aviva (AV -1.48%).

Deservedly bottom
Still deserving of its bottom spot is International Consolidated Airlines Group (IAG -0.45%). Its complicated structure must be a real constraint. IAG is a holding company, but British Airways and Iberia each have their own boards, which retain considerable autonomy.

CEO Willie Walsh came to the job with a great reputation forged at Aer Lingus and BA, but it remains to be seen whether he will have the clout to successfully take on the Spanish unions. The mixed results of a successful year at BA and underperformance at Iberia resulted in Walsh earning less last year than BA's head.

All change
RBS was originally marked-down for the paucity of directors' shareholdings, but CEO Stephen Hester now has half a respectable worth of 1.5 million pounds. Finance director Bruce Van Saun still has just a 140 thousand-pound holding. RBS would also now get higher marks for performance, having demonstrated considerable progress in cleaning out its balance sheet, and successfully floating Direct Line last year.

Barclays was the first company I looked at in this series, and its board has changed beyond recognition in that time: a new Chairman, a new CEO, and a change of guard among the non-execs. Oh, and the finance director is to step down: He's just waiting for a successor to be appointed. Barclays has a newfound morality (we're told) and a new strategy under CEO Anthony Jenkins.

Unpopular
Things have also moved quickly at Aviva, where chairman John McFarlane shook the company up, including the sale of the its U.S. unit. He recruited CEO Mark Wilson, who restructured management -- in the process he dispensed with the services of Trevor Matthews, who had been recruited with a golden hello of 2 million pounds just a year earlier. A surprise dividend cut has made the pair unpopular with investors.

Marks and Spencer's (MKS 1.12%) CEO Marc Bolland is three years into a turnaround program at the company, but though he's reinvigorated its food offering, its non-food sector is hurting. Some fund managers have suggested that this year's autumn clothing range will determine whether Bolland remains in fashion himself.

I've collated all my FTSE 100 boardroom verdicts on this summary page. I hope my research can assist you in your investment decisions.

Buffett's favorite FTSE share
Legendary investor Warren Buffett has always looked for impressive management teams when picking stocks. His latest acquisition, Heinz, has long had a reputation for strong management. Indeed, Buffett praised its "excellent management" alongside its high-quality products and continuous innovation.

So I think it's important to tell you about the FTSE 100 company in which the billionaire stock-picker has a substantial stake. A special free report from The Motley Fool -- "The One U.K. Share Warren Buffett Loves" -- explains Buffett's purchase and investing logic in full.

And Buffett, don't forget, rarely invests outside his native United States, which to my mind makes this British blue chip -- and its management -- all the more attractive. So why not download the report today? It's totally free and comes with no further obligation.