They have been described as "biased" and "oligarchic".
Standard & Poor's (S&P), Moody's Investors Service and Fitch Ratings, the big three credit-rating agencies, have come under fire from Madrid to Manama.
Q&A: Credit ratings
Who are the main credit-rating agencies? Standard & Poor's, Moody's Investors Service and Fitch Ratings are the three big agencies that dominate 90 per cent of the ratings industry.
What do credit-rating agencies do? Ratings agencies carry out credit checks on companies and countries before either can borrow from financial markets.
Why are they so influential? Investors use credit ratings to help them decide whether to buy bonds and other financial products from companies or governments.
How do ratings agencies make money Companies pay agencies to provide them with a rating of their creditworthiness, enabling them to tap financial markets.
And some of the most vehement criticism has come from Wolfgang Schaeuble, the German finance minister.
"We must break the oligopoly of the ratings agencies," he said this month as the euro-zone debt crisis threatened to spiral out of control.
Jose Manuel Barroso, the European Commission president, went further. "There may be some bias in the markets when it comes to the evaluation of Europe," he said.
The actions of credit-rating agencies have long moved financial markets and caused sleepless nights for government officials and business executives.
But the big three have dominated the headlines more than usual after they downgraded the credit ratings of countries embroiled in the euro-zone turmoil and warned the US it would lose its top rating if it did not resolve the deadlock over the debt ceiling.
Eighteen months earlier, it was Dubai's turn to come under the microscope, when trouble with debt triggered downgrades of several corporations.
"I would not be surprised if, going forward, there would be some sort of realignment of rating agencies in terms of their role, mandate and structure," says John Sfakianakis, the chief economist at Banque Saudi Fransi.
By determining the risk of a country or company defaulting on its debts, credit ratings significantly influence the cost of raising funds.
With the region's governments and state-backed companies raising tens of billions of dollars a year on financial markets, ratings can have huge implications for the economy.
For years, agencies and investors had assumed the UAE Government would come to the rescue of troubled government-related companies. But Dubai World's US$24.9 billion (Dh91.45bn) debt restructuring triggered a change to that mindset.
Elsewhere in the Middle East, agencies have been busy after unrest in some countries. Sovereign downgrades sounded a note of caution amid a surging tide of optimism about the future during the so-called Arab Spring.
The ratings of Egypt, Tunisia, Libya, Jordan and Bahrain were lowered this year. Bahrain took exception, with officials in the kingdom asserting that the downgrades were based on flawed information and politicised reports.
The Middle East has endured an uneasy relationship with agencies in recent years. The global economic downturn made it harder for firms to raise debt, eventually straining relations between companies seeking funds and the agencies they hired to gauge their creditworthiness. Abu Dhabi National Energy Company (Taqa), a government-backed energy investor, in 2009 ended its relationship with S&P after the agency put the company on credit watch.
Despite the global criticism, the rating agencies remain bullish on their role in the markets.
"Our role is to call credit risk as we see it and to explain our views clearly, without fear or favour. That is what investors expect us to do and that is what we are focused on doing," says Martin Winn, S&P's vice president of communications in Europe, the Middle East and Africa.
The big three were also criticised for downgrading Greece and other indebted euro-zone countries such as Portugal.
They were also slammed during the global financial crisis for giving high ratings to subprime mortgage-based products that turned toxic, and as being too slow in warning investors.
This led to new rules in the EU designed to more closely regulate how the agencies work.
In the Middle East, calls have been made in some quarters to set up a home-grown agency to challenge the dominance of the big three. A regional organisation may have a better understanding of the structure of companies with government backing, the argument goes.
"Rating analysts are based in this region after previously being based in the London or New York, so there's probably a better understanding of the economics of the region, the companies of the region," says Nasser Saidi, the chief economist and head of external relations for the Dubai International Financial Centre Authority.
"Having said that, having more local rating agencies is important primarily because many companies are relatively small, and international rating agencies are only focused on the large companies. Having local rating agencies will mean the coverage is much wider and you'd have much more coverage of mid-size companies."
