Vadra arrived at the ED's Jamnagar House at 3.45 p.m. and left at 9.35 p.m. He was accompanied by his wife and Congress general secretary for Uttar Pradesh East, Priyanka Gandhi Vadra.

She, however, left the ED office after dropping Vadra, who was questioned by the investigating agency for the first time.

A team of seven ED officials of the rank of Deputy Director and Assistant Directors took part in his questioning.

According to an ED official, Vadra was asked questions relating to transactions, purchase and possession of certain immovable assets in London.

The ED's case relates to the ownership of 1.9 million pounds of undisclosed assets abroad, allegedly belonging to Vadra.

Soon after Vadra's questioning, his lawyer Suman Jyoti Khaitan told reporters "they wanted to harass him as part of political vendetta".

"He (Vadra) felt that something wrong is going to happen. He on his own went to the court and said he is going to appear voluntarily before the ED. He asked the court to give him the date to appear before the ED. The court gave today's date. He appeared before the ED on his own even without receiving summons.

"He answered every question he was asked. The matter is sub-judice, I cannot tell more. We have given the undertaking," Khaitan said.

Agency sources said that Vadra has been asked to join the investigation again at 10.30 a.m. on Thursday.

The ED has lodged a money laundering case against Vadra's close aide Manoj Arora after his role surfaced during a probe by the Income Tax Department into another case under the new Black Money Act and tax laws against absconding arms dealer Sanjay Bhandari.

The London property was allegedly bought by Bhandari and sold in 2010 for the same amount despite incurring additional expenses on its renovation.

On December 7, as part of the investigation, the ED conducted searches at a number of premises in Delhi-NCR and Bengaluru.

The ED counsel has told a city court earlier that the London property was part of the kickbacks received in a petroleum deal. The money was transferred by Santech International, FZC, a UAE-based company controlled by Bhandari.

There were a few more properties that needed to be probed, the counsel said.

The official said that Arora, an employee of Vadra's Skylight Hospitality LLP, is a key suspect in the case as he is aware of the overseas investments and purchases made by his employer.

He also said that the agency also confronted Vadra with the statement given by Arora.

The questioning came in the wake of an order by a Delhi Court on February 2 directing Vadra to appear before the ED for questioning while hearing the anticipatory bail plea filed by him.

The court had on Saturday also granted interim bail to Vadra till February 16.

Earlier in the day, Priyanka Gandhi Vadra, who accompanied her husband to the ED office made a strong political statement.

"I stand by my family," she later told reporters at the AICC headquarters where Congress workers shouted slogans hailing her. "Priyanka you fight on, we are with you!"