BJP had appointed the task force on unravelling the amount of black money stashed by Indians in foreign banks and ways to bring it back.
The report had alleged that Sonia Gandhi and former prime minister Rajiv Gandhi were among Indians who held Swiss bank accounts.
This had led Sonia Gandhi to write a letter to Advani denying the allegation.
Sources said in the letter, Gandhi had said that neither she nor her husband held Swiss bank accounts.
In his reply to the Congress president`s letter, Advani expressed regret of her name and that of her late husband being mentioned in the task force report.
However, Advani also stated in his reply that the Gandhis should have denied this publicly when there were murmurs that names of her family members could figure in the report.
Advani said had she done so, the name of her family members would not have figured in the task force.
The four-member task force comprising S Gurumurthy, former IB director Ajit Doval, Professor R Vadiyanathan and advocate Mahesh Jethmalani has put the figure of money stashed in safe havens to be 25 lakh crore.
On February 1, NDA leaders had released a booklet `Indian Black Money Abroad in Secret Banks and Tax Havens`, the second report of the task force appointed by the BJP.