This decision is "shocking, because it brings politics into sport... We are totally against that. And Malek is the first victim, because tennis is his career, his bread-winner," Amir Jaziri told AFP.
"To be clear, Malek pulled out for sporting reasons, because he was injured. He did his warm up, something was wrong and the doctor found that his knee was swollen," he said.
When Jaziri withdrew from Friday's match against Weintraub, in the quarter-final of the Challenger tournament in Tashkent, he also cited knee problems.
"But at the political level, we received an order not to play. It was an email from the Tunisian Tennis Federation, via the national technical director," Amir continued, detailing the contents of the email.
"'After the meeting at the ministry of youth and sports with Riadh Azaiez, I regret to inform you that you cannot play,'" he said, quoting the email, and referring to the director of the country's sporting elite at the ministry.
Both Jaziri, who is currently ranked world number 169, and Weintraub are members of the same top-flight tennis club in France - Sarcelles Tennis - north of Paris and have known each other for years through their sport.
Contacted by AFP, the club's president Jonathan Chaouat said Jaziri was in fact the reason for Weintraub's recruitment by the club.
The 29-year-old Tunisian, who has declined to talk to the press since withdrawing from the tournament in Tashkent, could have risen to 135th had he won.
'Part of electoral campaign'
The ministry insisted that it had nothing to do with the order instructing him not to play, stressing that the decision came from the tennis federation.
Amir said he didn't know whether his brother would have played the match if he hadn't been suffering from a knee injury.
But he said he failed to understand how such an order could be given after Malek had already played Weintraub and "Tunisia has played Israel in the 2009 Fed Cup."
"Tennis doesn't normally get much media coverage in Tunisia. What happened was only done as part of an electoral campaign, and everyone profits (electorally) from this," Amir Jaziri charged.
The country has been locked in a political crisis since the summer due to deadlocked negotiations between the ruling Islamist party and the opposition.
But parliamentary and presidential elections are expected to take place in the coming months, if the rival factions manage to reach an accord on an interim government.
Tunisia has historically supported the Palestinians in their struggle with Israel, hosting Yasser Arafat's Palestine Liberation Organization between 1982 and 1994 after it was expelled from Lebanon.
And the political pressure on Malek Jaziri has failed to spark outcry in Tunisia, with some media actually hailing his decision to concede the match.
"He has lost ATP points (in the world rankings) but won respect and preserved his honor," said Tunisian daily La Presse.
"History only remembers courageous decisions. Jaziri made the right choice," it added, describing the player's knee injury as "diplomatic."
The incident was not without precedent in Tunisia.
Last April, the sports ministry recalled the national Taekwondo team after it met Israeli sportsmen at a competition in Belgium.
"The ministry ordered an immediate inquiry because of the encounter between members of the national Taekwondo team and the Israeli team in an international competition abroad, without consulting the relevant authorities," the ministry said at the time.
But it never announced the result of the inquiry.
The Tunisian authorities have never officially banned sporting encounters with Israeli nationals, and since Jaziri's decision to withdraw from the tennis tournament in Uzbekistan no such directive has been made public.