By Raymond Colitt

BRASILIA (Reuters) - Opposition leaders demanded an inquiry on Monday into a report that Brazil's intelligence agency spied on the Supreme Court chief and members of Congress, in the latest scandal to hit President Luiz Inacio Lula da Silva's government.

The scandal is unlikely to dent Lula's strong approval ratings, buoyed by a booming economy, and his government said the alleged spying was "abominable," but it could sour his relations with Congress and the judiciary.

Veja, the country's leading news magazine, reported on the weekend that the Brazilian Intelligence Agency, or Abin, spied on Supreme Court President Gilmar Mendes and tapped his telephones. It published what it said was a transcript of a private telephone conversation Mendes had with a member of Congress.

An Abin agent who provided the transcript said such illegal phone tapping of authorities was common and also included the head of the Senate and two cabinet members, Veja reported.

Lula held urgent talks for most of Monday with Mendes, the Senate speaker and several Congress members who expressed their concern and demanded those responsible to be punished.

"Somebody has to be sacked. If the justice minister is at fault, let it be him then," said Demostenes Torres, of the opposition DEM party.

Lula was surprised and outraged at the possibility of the Supreme Court chief being secretly recorded, his spokesman Marcelo Baumbach told reporters.

Abin said it was investigating the accusations but had confidence in its staff.