Greece, Bulgaria, Poland and Romania are the worst European Union countries at delivering justice through criminal trials, according to an independent survey of the union's courts.

States on the eastern fringes of the union emerge as serial offenders in a comparative study of breaches of individuals' right to liberty and a fair trial recorded by the European court of human rights (ECHR).

Delays in bringing cases to trial were the most common reason for critical judgments. In some EU countries pre-trial detention can last for up to four years; others have no legal maximum.

The figures, collected by the London-based organisation Fair Trials International and the international law firm Clifford Chance, cover a five-year period between 2007 and this summer.

The problems appear to be getting worse. There were 37 violations of the right to a fair criminal trial in EU states in 2007, and 75 in 2011 – an increase of more than 100%.

Greece had the highest number of violations – 108 – for breaching both articles over the five-year period. Most relate to chronic delays in bringing cases to trial. Interpreters are not always available and concerns have been raised about judicial corruption in Greece, the study, Defence Rights in the EU, warns.

Bulgaria had 92 violations recorded by the ECHR, most of them also due to inordinate delays. Those detained are often not given sufficient access to lawyers or their family, the report finds.

Poland, with 67 breaches, fell foul of the Strasbourg court's requirement that there should be legal advice for defendants and because of lengthy legal postponements. Too many people are routinely detained in custody and denied access to court files during investigations, the study adds.

Romania, with 49 violations, was criticised for failing to allow detainees to challenge the legality of their detention, be presumed innocent until found guilty and question witnesses giving evidence against them.

The UK figures of 12 violations over the five years, with fewer recorded breaches than Italy and France, is relatively low. That figure will confound eurosceptics who claim that the Strasbourg court is unreasonably critical of British justice. Conversely, it will bolster the UK government's argument that the court should concentrate on those countries whose legal systems consistently cause the most problems.

Adjusted for population size, the United Kingdom in 2011 had one of the best records in adhering to acceptable standards set out in article 5 (the right to liberty) and article 6 (the right to a fair trial) of the European convention on human rights. Tiny Malta and Latvia stand as the worst two offenders.

The pattern of legal failures roughly reflects the economics of the continent, with poorer states least able to deliver fair and timely justice. Fair Trials International has used the information to produce a map which assesses each EU state in terms of its criminal law difficulties.

Jago Russell, chief executive of the charity, said: "Suspects' rights are being violated in police stations, courtrooms and prisons across Europe. In a European Union founded on the rule of law and respect for basic human rights, these abuses cannot be allowed to continue.

"The EU has a crucial role to play in raising standards of justice in Europe, but if it fails to act now, citizens' faith in EU laws like the European arrest warrant will be undermined."

Fair Trials International is calling for a common EU standard on how long anyone can be remanded in custody before being brought before a court.