According to media reports, 74-year-old Mumtaz also denounced Asif Ali Zardari, Benazir's widower and the new co-chairman of the Pakistan People's Party (PPP), as an opportunist and said that he doubted the authenticity of the 'will' that Bilwal, the 19-year-old son of the former leader, read out at the family home on Sunday.

The PPP said that the 'will' nominated Zardari as Benazir's successor, but he immediately stepped down in his son's favour, on the understanding that the father would run the party until the son had completed his studies at Oxford in three years.

Bilawal, who flew to Dubai early Tuesday, changed his name on Sunday from Bilawal Zardari to Bilawal Bhutto Zardari in a symbolic move asserting his right to lead the Bhutto dynasty.

"You can't just add a name. You can't become a Bhutto overnight," Mumtaz told The Times at the original Bhutto family home, 3 km from the mausoleum where Benazir was buried alongside her father and two brothers on Friday.

"It's very suspect", he said. "Suddenly a will has come into existence that nobody has seen before."

Mumtaz - first cousin of Zulfiqar Ali Bhutto, Benazir's father - said that the name change violated tribal norms and that Bilawal had no right to lead the party as he was not a Bhutto.