But a spokesperson for UOHC, an umbrella group that represents strictly Orthodox shuls, said some had taken "advantage of the Rov's current poor health" in what was a "truly shocking" case.
"It is truly shocking that [those behind the letter] would seek to take advantage of the Rov's current poor health by deceiving him into signing a letter that has now been twisted into an endorsement of Jeremy Corbyn and circulated widely by Mr Stern," the spokesperson said.
"The Rov's position is clear in that he does not involve himself in such partisan political matters. This has always been the mesorah (tradition) of the Rov and indeed the Rov’s late father.”
The UOHC initially claimed Shraga Stern, a prominent anti-LGBT education activist from the Charedi community, was involved in the letter.
When contacted for comment, Mr Stern denied this. "I had nothing to do with it," Mr Stern said.
The UOHC later issued a second statement that appeared to withdraw the allegation against him, referring instead to "a few irresponsible hotheads".
The JC understands the UOHC is investigating who was responsible.
Mr Stern referred the JC to another Charedi rabbi, Rabbi Tambur, who said he asked Rabbi Padwa to sign the letter because he feared the Jewish community would be attacked if Labour lost Thursday's General Election.
"Whether Labour win or they lose, we are worried about it being a danger for us. If they win, it's a danger for us. If they lose, it's a danger. We'll be blamed either way," he said.
He claimed Rabbi Padwa had advised him on the contents of the letter before changing his mind about it being released. "Someone leaked it after that," he said.
