A former aide to Sen. Herman E. Talmadge (D-Ga.) amassed a personal net worth of nearly $1 million and had thousands of dollars in unaccounted-for deposits in his bank account in 1974, Talmadge's attorney said yesterday.

The allegations were made by James Hamilton, Talmadge's attorney in the probe of the Georgia senator's finances by the Senate Select Committee on Ethics. Hamilton spoke during a preliminary session to settle procedural matters before the committee begins its full-scale public hearing of Talmadge's case next Monday.

Hamilton told the committee during yesterday's open session that "a third party" whom he declined to identify sent Talmadge a February 1976 financial statement indicating the senator's former aide Daniel Minchew was worth nearly $1 million.

Minchew, who is the chief witness against Talmadge, has submitted financial records of his own to the committee. His attorney, Robert Fierer, said after the committee session that he could not recall seeing any statement listing Minchew's worth at over $500,000.

Fierer also challenged the statement by Hamilton that Minchew had failed to account for thousands of dollars in deposits into his bank account in 1974.

Talmadge, a 23-year Senate veteran, is accused of filing false Senate expense claims and converting campaign contributions to his personal use. He has also been accused of hiding some of the money in a secret bank account here. Talmadge has denied the allegations.

Minchew, Talmadge's chief aide until 1974, has been called an "embezzler" by the senator. Minchew has admitted receiving as much as $10,000 from the secret account. But he said the money was mostly used to reimburse him for expenses incurred on behalf of Talmadge. He has said Talmadge knew of the secret account and benefited from it.

Both Minchew and Talmadge have had their financial records closely audited by Senate ethics investigators who had been searching for unaccounted-for sums of money. Earlier this month Talmadge's former wife, Betty, told the investigators that for years her husband kept a cache of $100 bills in an overcoat in their Washington apartment.

The committee yesterday rejected Hamilton's plea for a postponement of the hearing. Hamilton said he had been denied some of Minchew's records, but committee Chairman Adlai E. Stevenson III (D-Ill.) ruled that the hearing would begin Monday as planned.