VIENNA, May 22 (Reuters) - The founder of the crumbling Signa property empire, Rene Benko, made a rare public appearance on Wednesday to face Austrian lawmakers' questions over possible government favours, but declined to answer many of them.

Benko, 47, became a self-made billionaire by building Signa from the ground up, leveraging units heavily in an era of super-low interest rates that began to end in 2022. As rates kept rising, key parts of Signa declared insolvency this year.

Signa is now the biggest casualty of Europe's property downturn, and creditors are seeking to salvage what they can. Politicians have seized on its collapse ahead of a parliamentary election due to be held by October.

"Do you know a boat by the name of Roma?" lawmaker Kai Jan Krainer of the opposition Social Democrats (SPO) asked Benko at a parliamentary commission hearing on Wednesday during a particularly lengthy exchange.

"What does that have to do with the matter being investigated?" Benko said.

"I think you know," Krainer replied.

Krainer said it was a yacht that hosted ministers from the conservative People's Party (OVP) in 2017. Benko said Signa had often rented it and, while he could not remember whether specific ministers had been on it, he could not rule it out either.

Throughout the hearing, Benko often conferred at length with his lawyer before answering.

The commission, set up by the SPO and the far-right Freedom Party, is investigating a potential "two-class administration due to preferential treatment of billionaires by OVP members of government", specifically regarding aid given to companies in the COVID-19 pandemic. The OVP denies wrongdoing.

Opposition parties describe Benko as close to the ruling OVP, particularly its former leader Sebastian Kurz. The OVP often targets former Chancellor Alfred Gusenbauer of the SPO, who was a senior Signa executive until this year.

Benko said Signa had hosted Kurz at a large summer party on Lake Garda in Italy in 2017 when he was foreign minister. He also said that years later in 2023 he had sent Kurz the resumes of two central-bank officials looking into Signa's finances.

Benko frequently cited ongoing criminal investigations as a reason for not answering.

Prosecutors have placed Benko under investigation on suspicion of fraud. He also said he is a suspect alongside Kurz in a sprawling corruption investigation that forced Kurz to quit as chancellor in 2021. (Reporting by Francois Murphy Editing by Christina Fincher)