The Electoral Commission said there was a political "void" in some communities and this void was being filled with "ethnic kinship networks" which could undermine the principle of free choice for voters.
The Commission has set up an enquiry, earlier this month, to examine the vulnerability of some South Asian communities, specifically from Pakistan and Bangladesh, to electoral fraud.
It concluded that British-Pakistanis and Bangladeshis were "vulnerable" to ballot-rigging because of a lack of campaigning activity by the mainstream political parties.
"Our analysis strongly indicates that the primary source of this influence of kinship networks in politics lies in the lack of mainstream political party activity in the areas of concentration of Pakistani and Bangladeshi voters," their report concluded.
More From This Section
It added: "This political void is filled by the ethnic kinship networks, which perform a role of a mediator between the British electoral system and immigrant-origin communities.
"Mainstream political parties were deemed by our interviewees to be only too happy to accept this middle-man role of kinship networks," it added.
It found that women and young adults in such communities were increasingly raising concerns about the role played by the ethnic networks concerning their voting choices, with some complaining they were being "outright disenfranchised".
The commission said it was working closely with police in areas with a history of ballot-rigging to put in place additional measures to prevent problems at the general election in May.
Electoral Commission chairperson Jenny Watston said that when fraud was committed, candidates and campaigners were the most likely offenders and voters the victims.
There are over a million British-Pakistanis and they form the second largest ethnic-minority population in the UK. There are also about 5,00,000 Bangladeshis residing in the UK.