Rajani Pandit has been conducting covert operations for over 30 years out of her small office in Mumbai.

As India's best-known female private eye, she has posed as crazy, blind and deaf to solve murders and unmask unsuitable fiances. But election time is boom time for the woman dubbed "Miss Marple".

In the world's biggest election ending on Sunday, Ms Pandit and others like her are in high demand from political parties to dig up dirt on the opposition and make sure their own candidates are squeaky clean.

"It's confidential but whenever a party finds one of its own candidates or an opposition candidate suspicious they ask us to investigate them," Mumbai-based Ms Pandit told AFP.

"Often we are asked to look into their finances and how they have procured money to fund their campaigns. We try to maintain a low profile," the 57-year-old added.

Inundated

Prime Minister Narendra Modi is up against Congress leader Rahul Gandhi in the world's largest democratic exercise. Some experts say the polls could cost $10 billion.

Ms Pandit says her team has been busy "integrating" themselves into political parties since January, inspecting finances and attending rallies before submitting reports to their clients.

"There's usually a surge of cases ahead of the elections. We've been inundated with requests and were only able to take on a few," she said.

Kunwar Vikram Singh, chairman of India's Association of Private Detectives and Investigators, said "there's a lot of due diligence".

"(A candidate's) local reputation, influence, his stance in his own caste... all these things are looked into," Mr Singh told AFP.

Magnifying glass

Private detective agencies are popular in India, with sleuths tasked with solving everything from petty household thefts to business deals gone wrong.

Ms Pandit has been conducting covert operations across India for over 30 years out of her small office in Mumbai.

The investigator -- who does own a magnifying glass -- was dubbed India's first female private detective by media outlets when she began cracking cases in the early 1980s.

Rajani Pandit says her team has been busy "integrating" themselves into political parties since January, inspecting finances and attending rallies before submitting reports to their clients.

She has been featured in countless newspaper articles, often referred to as India's "Miss Marple" or "Nancy Drew", Agatha Christie's fictional spinster sleuth and the ever-evolving US amateur detective.

This has encouraged scores of women to follow in her footsteps.

Several women-dominated investigative firms now operate in the country, such as Lady Detectives India and Venus Detective which are both headquartered in the capital New Delhi.

"Clients are open a lot more to having a female investigator. They feel we are more empathetic and that they can talk to us," Lady Detectives CEO Tanya Puri told AFP.

A suitable boy

Ms Pandit first started snooping as a 22-year-old at college, informing the parents of a fellow student that their daughter was drinking, smoking and hanging out with boys.

Her most difficult case was when she worked undercover for six months as a maid for a woman who was suspected of poisoning her husband to death and then killing her son through a hitman.

She gathered evidence and handed it over to police who arrested the hitman and the woman.

Ms Pandit has won numerous awards, written two books, and says she has completed more than 80,000 cases -- most of them pre-matrimonial investigations.

Parents in India seeking a suitable husband or wife for their children will ask her to investigate the potential spouse and their family.

She looks into whether they have the job they say they have and tries to find out if there is anything in their past that might be deemed to bring shame to the family they are marrying into.

Ms Pandit has had to be the master of subterfuge to gather evidence, including donning "various disguises". But she says she received no formal training.

"Detectives are born, not made. I will keep doing this job until I am no longer alive," she said.