The Price of the Vote documentary film, which aired on Thursday evening at a Budapest cinema and on YouTube, presents the results of a six-month investigation by independent filmmakers and reporters.

In the film, voters, mayors, former election officials and a police officer claim that large sums of money and even illegal drugs are being offered to pressure people to vote for Fidesz.

Fifty-three of Hungary's 106 individual constituencies and up to 600,000 voters are targeted, the film alleges – potentially 10% of the expected turnout of six million.

"In the beginning, we thought the key piece of this process is vote-buying. But then we realised that the money is just the icing on the cake. The key word here is dependency and vulnerability," Aron Timar, one of the filmmakers, told the BBC.

"The money comes in on a pretty serious scale, and with quite a large entourage," says one interviewee, a serving police officer whose face and voice is disguised, in the documentary.

"I didn't become a police officer to serve a corrupt system. To help cover things up."

In one village, the Fidesz mayor is also the district doctor for a catchment area covering 32 settlements. Patients say they fear they will not receive their prescription if they do not vote for the party.

Firewood is only distributed to those who vote for the party, several people interviewed claim.

In another, a former candidate dropped his bid for elected office, after the child protection office allegedly threatened to take his children into care.

The authorities did not want him running against the candidate preferred by the governing Fidesz party, he claims.