Arron Banks, who funded the Leave.EU campaign in last year's referendum, gave £1 million to Ukip ahead of the 2015 general election.
He has been involved in a public spat with the party's only MP Douglas Carswell and has been critical of the party's leader Paul Nuttall.
Mr Banks said his membership had lapsed and when he tried to reapply he was told he was suspended until an appearance before the party's ruling national executive committee (NEC).
But Ukip dismissed the idea he could have been suspended, as he was no longer a member of the party.
Mr Banks suggested on Twitter that the move was "apparently for saying current leadership couldn't knock the skin off a rice pudding" and he has also compared the way the party is run to a squash club.
His row with Mr Carswell, which included suggesting he could stand against the Clacton MP by using a recall petition to trigger a by-election, has also riled elements in the party.
Ukip refuted Mr Banks' claims, claiming instead that he chose not to renew his membership despite reminders to do so.
Mr Banks has hinted at setting up a new political movement, building on Leave.EU, to "drain the swamp" of Westminster politics.
He tweeted: "Ukip 2.0, the force awakens."
A Ukip spokesman said: "We are aware that Mr Banks has suggested on Twitter this morning that he has had his party membership suspended.
"Mr Banks was notified last year that his membership was due for renewal at the start of October but chose not to renew, despite reminders. With this his membership expired on January 1 2017.
"It would not be possible to suspend Mr Banks from something of which he is not a member."