Russia and Argentina have been named by a corruption watchdog as countries where political interference in the judicial process has risen recently.
Corruption erodes the rule of law, says Transparency International
Berlin-based Transparency International says corruption is also undermining justice in many parts of the world.
In a new report, the group says corruption is denying people the right to a fair and impartial trial.
Corruption also impedes economic growth by lowering the trust of the investment community, the report says.
"Equal treatment before the law is a pillar of democratic societies," said Huguette Labelle, head of Transparency International.
"When courts are corrupted by greed or political expediency," she says, "the scales of justice are tipped, and ordinary people suffer."
In its report, TI says that judicial systems are being corrupted in two ways - through political interference and bribery.
In 20 countries around the world more than 30% of households said bribery was involved in getting a "fair outcome in court", TI reported.
In Africa and Latin America, about one in 5 people paid a bribe, compared to 15% in "newly independent states" and the Asia Pacific, 9% in South East Europe, 2% in North America and 1% in the European Union and other Western European countries.
In 20 countries, more than 30% said bribery involved in getting "fair outcome" in court
In Russia, an estimated $210m paid in bribes to courts annually
In Pakistan, 96% of people surveyed found courts corrupt
Source: Transparency International
According to a 2002 survey, an estimated $210m (£105m) in bribes is spent on Russian law courts each year.
As an example of political interference in Russian courts, the report says a judge in Moscow was dismissed after she said she had been pressured to decide in the prosecutor's favour in an interior ministry investigation.
Transparency International quotes the judge in question, Olga Kudeshkina, from a letter she wrote to President Vladimir Putin.
She wrote that Moscow's judicial system was "characterised by a gross violation of individual rights and freedoms, failure to comply with Russian legislation, as well as with the rules of international law".
Ms Kudeshkina also said the chairperson of the court that sacked her could behave in that manner because of backing from officials in the Kremlin.
Argentina's political veto
Argentina's judicial council, meant to safeguard the independence of the judiciary, has been gradually politicised, says TI.
President Nestor Kirchner has reduced the size of the council, ensuring that political representatives on the body make up the majority. The quorum was reduced, giving the politicians veto power over the body's decisions.
TI also cites the example of a judge appointed by the former President Carlos Menem who ruled that excessive campaign spending by the ruling party had not broken the law.
Despite widespread problems with corruption in Africa, especially Zimbabwe, the report finds examples in Nigeria where trial times have been improved and judges are more rigorously screened before being appointed.
In Sierra Leone, non-governmental organisations have scrutinised and improved on some questionable practices of local customary law.
The report makes a number of recommendations to strengthen judicial independence and combat corruption:
- Judicial appointments should be made by independent bodies
- Judges should be appointed on merit
- Judicial salaries should reflect experience and performance
- Judges should be liable to prosecution if corruption is suspected
- Allegations against judges should be investigated by an independent body
- Judges should be removed or transferred in a transparent manner according to fair standards.