MADRID — Prime Minister Mariano Rajoy of Spain pledged Saturday to provide “complete transparency” about his financial assets and those of other politicians in his party to rebut what he described as “apocryphal” documents showing that he and others had received regular payouts from a secret parallel account maintained by the party.

In a televised address, Rajoy said he regretted the damage the corruption accusations had caused to his image — and to the image of his governing Popular Party and Spain as a whole — at a time of economic and social hardship. But he predicted “this is as far as it will go,” adding, “This party will defend itself.”

Rajoy also insisted his party had no connection to the $29 million amassed in Swiss bank accounts by a former party treasurer, Luis Bárcenas, who has been at the heart of the widening corruption scandal. His party, Rajoy said, “never gave orders to open accounts in a foreign country.”

The prime minister said he would publish online his tax returns this week. As to the financial rectitude of his colleagues, Rajoy said “all our tax contributions have been made within the strictest legality over all these years.”

Analysts said Rajoy’s TV speech was unlikely to contain a spreading graft scandal on which the courts have yet to rule.

“The earthquake will continue because more damaging information is likely to come out and the only way to put an end to such a scandal is to have a clear court ruling, which sadly in this country could take years,” said Antonio Argandona, a professor of economics and business ethics at the IESE Business School in Barcelona.

The scandal has come as another blow to Spaniards who have had to tighten their household budgets under Rajoy’s austerity program.