India's election commissioner today banned the counting of votes in the district where Prime Minister Charan Singh is a candidate as a result of reports that large numbers of untouchables were kept from voting.

The election commissioner, A. L. Shakdher, ordered a new vote in one polling place in the village of Katha, about 25 miles east of here, where newspaper photographs showed underage boys being allowed to vote while untouchables were kept from the polling booth.

Charan Singh, 77-year-old caretaker prime minister, is a member of the Jat castle of small landowning farmers, and his campaign has been based on giving more power to them at the expense of the untouchables -- India's lowest caste.

His major opponent for votes that will not go to the front-running candidate, Indira Gandhi, 62, comes from the Janata Party of Jagjivan Ram, 71, who is the leader of India's 100 million untouchables.

Ram, who has never identified himself with untouchable issues, and Gandhi, who in the past has won wide support from untouchables, are vying for the votes of India's lowest caste.

The counting of the ballots in the district of Baghpat, where Singh is running from, will not be done until a new vote is held in the polling place in Katha where the irregularities were reported.

Only a portion of India's 362 million eligible voters cast ballots Thursday.The rest go to the polls Sunday; the counting of all ballots starts then, with the first results scheduled to be released that night.

This election, more than any of India's previous six general elections, has been marked by blatant appeals along caste and religious lines.

Singh's Lok Dal Party, a breakaway from the Janata, gets its main support from small landowning farmers who have gained some economic power but still lack political clout.

The untouchables, through affirmative action programs started under British rule, have managed to get a measure of political influence through positions reserved for them in universities, the Civil Service and Parliament. But economic power largely has escaped them.

This fight for power -- political on the part of the small farmers and economic on the part of the untouchables -- has led to increased violence between castes during the past two years.

In some villages, untouchables have been thrown off their land. Officials in states such as Tamil Nadu, in south India, report an increase of crimes against untouchables from 18 in 1976 to 130 in 1978.