Political instability and a worsening economic outlook mean major emerging markets such as Argentina, Brazil and Russia are riskier places to invest, according to a closely watched index.

According to asset manager Blackrock's quarterly Sovereign Risk Index, the three months to the end of June favored developed markets such as Belgium and Britain, which rose in the rankings, while key emerging markets fell.

Brazil dropped four places to 31st out of 50 countries, attributed by Blackrock to rising levels of short-term debt. Russia fell three places to 24th, on "a decline in its perceived government effectiveness" and worsening economic prospects.

Argentina, locked in a row with investors refusing to accept write downs of sovereign debt arranged as part of a restructuring, fell one spot to 45th from the previous quarter.

The index is made up of a mix of quantitative measures, such as debt to gross domestic product (GDP) and tax revenues, alongside qualitative assessments like the perceived effectiveness and stability of governments.

Investors and economists have become increasingly concerned about political instability in many emerging markets following flare-ups of civil unrest in a lengthening list of countries such as Brazil, Thailand, Egypt and Turkey.

Blackrock set up the index in 2011, after the credit crunch and against the backdrop of a debt crisis in the euro zone that centered on Greece, seeking to provide investors a more in-depth measure of how risky sovereign debt was.

But while some emerging markets slipped in the rankings, a number of developed economies' rankings in the index benefited from the International Monetary Fund raising growth forecasts.

Belgium moved up four places to 27th, Britain rose three to 20th and the Netherlands moved up two to 11th.

(Blackrock Sovereign Risk Index country rankings, Top 10 and Bottom 10, June 2014:)

1 Norway 41 Ireland 2 Singapore 42 Hungary 3 Switzerland 43 Slovenia 4 Sweden 44 Italy 5 Germany 45 Argentina 6 Taiwan 46 Portugal 7 Finland 47 Ukraine 8 Canada 48 Egypt 9 New Zealand 49 Venezuela 10 Australia 50 Greece