BUCHAREST (Reuters) - Romania’s lower house of parliament on Monday night approved amendments to the country’s criminal procedure, which critics and the centrist opposition say would weaken prosecutors’ powers to probe high level corruption.

The new penal handbook designed by the ruling Social Democrats was endorsed in a 175/78 vote by legislators in a speedy procedure. Opposition groups say they plan to challenge it at the constitutional court.

Under the bill, courts of appeals would be barred from convicting a person found innocent by a lower court, unless new evidence is brought by prosecutors. Wire tapping that is not connected with the criminal deed by a person under investigation will no longer be taken into account.

The changes also set a maximum length for a criminal investigations to one year, which critics have said would effectively kill the country’s tangled web of graft cases.

Romania is one of the European Union’s most corrupt states and Brussels keeps its justice system under special monitoring since its 2007 accession into the bloc. The argument over how hard to fight graft has dominated its post EU-entry politics.

Anti-corruption prosecutors have secured a spate of convictions against lawmakers, ministers and mayors in recent years, exposing conflicts of interest, abuse of power, fraud and the awarding of state contracts in exchange for bribes.

But leading politicians, some of whom are currently under investigation or on trial, have denied wrongdoing and accused prosecutors of using their powers for political persecution.

Social Democrat leader Liviu Dragnea is barred from becoming prime minister due to a prior sentence in a vote-rigging case.

At the start of 2017, attempts by Dragnea’s ruling coalition to weaken anti-corruption legislation triggered the country’s biggest protests in decades.