Aung San Suu Kyi's political party complained on Monday of irregularities and rule breaches that could threaten the validity of a crucial upcoming by-election for seats in Myanmar's parliament.

The National League for Democracy (NLD), which will run for 47 of the 48 available seats, said potential voters had been left off the electoral roll -- almost 1,400 in Suu Kyi's constituency alone.

The NLD ended a boycott of Myanmar's military-crafted political system in November to run in the April 1 polls. It accused the powerful ruling party, which has close ties to former military dictators, of pressuring voters to attend its meetings and said one of its candidates had publicly slandered Suu Kyi.

At this point, the voter lists in some constituencies were found to be incomplete and full of errors, the party said in a statement.

It is hereby announced that these incidents can affect the emergence of a free and fair election.

The by-elections, to fill seats vacated by lawmakers appointed to cabinet or other top government posts, are pivotal for the year-old civilian government, which is eager to push the country's democratic credentials after 49 years of isolation and direct military rule.

Western countries have strongly hinted that some sanctions, which have blocked billions of dollars of foreign aid and investment from flowing into the impoverished country, could be lifted if the polls are deemed free and fair.

Suu Kyi and the NLD's participation marks a strong endorsement of Myanmar's political facelift and a warming of ties between the opposition and the military elite, much of which still wield power, having officially retired from their armed forces careers to join parliament and the government.

Citing examples of irregularities, the NLD said 54 villages in Suu Kyi's constituency of Kawhmu, south of the commercial capital Yangon, had a total of 413 dead people on the list of voters.

It said 1,387 eligible voters had been left off, while in the administrative capital Naypyitaw, a stronghold of the Union Solidarity and Development Party (USDP), voter lists had not been made available to the candidates.

The international community has called for transparency in the polls but so far, no announcement has been made as to whether observers or monitors will oversee it.

(Reporting by Aung Hla Tun; Editing by Martin Petty and Daniel Magnowski)