More than a sixth of candidates in the Indian elections have criminal cases pending against them, according to a think tank.
The Association of Democratic Reforms (ADR) said some candidates are facing allegations of murder, kidnapping, extortion, trafficking and rape.
The group, which keeps track of national and state elections, political parties, contestants and legislators, found 1,398 of the 8,230 candidates (17%) are facing criminal charges - an increase of 2% compared to the last elections of 2009.
India's elections are the largest in the world, with more than 800 million voters eligible to take part in choosing MPs for 543 constituencies.
Voting has been taking place in nine phased stages, with the last round of voting due to take place on Monday.
Professor Jagdeep Chhokar, a founding member of ADR, told Sky News the number of prospective MPs facing charges was a "very serious" problem.
"It emanates from a mindset of political parties that winning the election by any which way is fair game," he said.
"If we have people in decision-making positions who have serious criminal cases pending against them, it is rather unfair to expect them to make decisions which are in the overall societal interest.
"The law breakers are becoming the law makers."
Almost half of the constituencies in the polls have three or more declared criminals running for office, ADR found.
![Indians Cast Votes On Biggest Polling Day](http://media.skynews.com/media/images/generated/2014/4/18/303430/default/v0/485286223-1-522x293.jpg)
During the parliament that has just concluded, the think tank found 30% of MPs had criminal charges against them.
The revelation that some candidates are facing rape charges comes at a time when India has been grappling with the issue of violence against women.
Widespread shock followed the brutal gang rape and murder of a 23-year-old physiotherapy student in Delhi in December 2012.
It resulted in new fast-track courts to try cases of crimes against women, as well as new laws and the toughening up of punishments for those found guilty.
However, the issue has taken a back seat since the start of the election campaign.
Mr Chhokar said: "It's very disheartening and disturbing to see that political parties don't see a rape case against a person as (warranting) a disqualification.
"The law says that unless a person is convicted, he or she is presumed to be innocent … but one would expect political parties (to) also look at the spirit of the law and rise above legal technicalities."
Mr Chhokar said he accepts some of the charges may be politically motivated but added all of them have reached the third stage of the criminal jurisprudence process, meaning a judicial officer has found enough evidence in the police investigations to frame charges in court.
The first election results are expected on Friday.