Joerg Haider and Stefan Petzner enjoyed electoral success
The new leader of the party previously headed by Austrian far-right politician Joerg Haider has admitted the two men had a "special relationship".
Stefan Petzner told Austrian radio that Mr Haider, whom he met five years ago, was "the man of my life".
Mr Haider, 58, died in a high-speed car crash earlier this month. He had a high blood alcohol level.
His party, the Alliance for Austria's Future, insisted on Thursday that Mr Petzner "wasn't his lover".
"He was a very good friend, it wasn't love," party spokesman Heimo Lepuschitz told the BBC, commenting on Mr Petzner's remarks.
The Alliance for Austria's Future is best known for taking a tough line on immigration and EU policies.
Mr Petzner took over as head of the party following his leader's sudden death.
Mr Haider had said frequently that he would like his 27-year-old protege, and party deputy to take his place one day.
But Mr Petzner, while remaining overall party leader, is now deputy to hotelier Josef Bucher in the party's parliamentary group.
Petzner says 'Haider was my best friend' on 11 October 2008
The party spokesman said Mr Petzner had not been criticised in the party for his comments and that it was Mr Petzner's suggestion to put Mr Bucher in charge of the parliamentary group.
Mr Petzner "will look after strategy as head of the party," Mr Lepuschitz told the BBC.
It has been widely reported in Austria that on the night of his death, Mr Haider left a bar where he had been drinking with Mr Petzner after they had argued.
' I loved him'
Mr Petzner has described feeling a magnetic attraction to Mr Haider.
"We had a special relationship that went far beyond friendship," Mr Petzner said in an emotional interview on Austrian national radio.
"Joerg and I were connected by something truly special. He was the man of my life," he added. "I loved him as a best friend."
There has been no comment from the Haider family. He was married with two children.
Joerg Haider became a potent force in Austria in the 1980s and 90s, championing what he called traditional family values and an end to immigration.
More recently his Alliance for Austria's Future enjoyed success at the polls, gaining more than 10% of the votes in September's general election.