A resident in Savile Town, Dewsbury, contacted a local councillor this week to claim that the postal voting system had been abused by a couple who had called at homes to check if forms had been completed.
The allegation is that unopened forms were handed over and then filled in.
The claims were passed onto Conservative councillor Khizar Iqbal who contacted the elections office of Kirklees Council and police were then called in.
Coun Iqbal said: “Both the police and Kirklees Council have confirmed they are taking it very seriously. The police assured me they will get to the bottom of this.
“I have been informed of this allegation; I have not witnessed it myself.”
He believes that postal voting fraud could be widespread but in this instance the allegation centres on a handful of postal voting forms in the Savile Town area, he added.
Coun Iqbal added; “This is about criminality, it is not about race or colour. The fact is the people doing this are defrauding the system.”
He has issued a campaign leaflet warning voters about the risks of going to prison if they commit electoral fraud.
“It is important we uphold the law and the integrity of the electoral process.
“The system is open to abuse but the majority of people respect the law and the integrity of the electoral system.”
A West Yorkshire Police spokesman said: “We have received an allegation of election fraud taking place in the Dewsbury South ward and are currently investigating the report. No arrests have been made and enquiries are ongoing.”
Adrian Lythgo, the Kirklees returning officer said: “I ensure that information is included in all postal vote packs advising electors about the regulations in relation to postal voting and what is and is not appropriate.
“The council, along with all other local authorities, has arrangements in place to monitor postal voting.
“It is not unusual for postal votes to be an area of interest and scrutiny but where specific information or allegations are received they are followed up in conjunction with the police.”