Mr Wheeler has said he will not appeal against the explusion.
A Conservative party donor expelled after he gave £100,000 to UKIP has accused Tory leader David Cameron of not being firm enough on Europe.
Stuart Wheeler said if he was elected Mr Cameron should pledge to hold a referendum on the Lisbon treaty.
He said if people voted against it the party should make "major changes" to the UK's relations with the EU.
But Mr Cameron said donors did not set party policy and said they "can't have" members donating to other parties.
He told the BBC Stuart Wheeler had "admirable qualities" and a "fine mind", but politics was a "team game and in the end, you're either in the team or not".
"So we had to say goodbye to him and his money," Mr Cameron told BBC radio.
He also rejected Mr Wheeler's suggestion that his position on European integration was "completely insufficient", saying that people should vote Conservative if they wanted a referendum on the treaty.
The spread-betting tycoon has given millions of pounds to the Conservatives, including a single £5m donation in 2001.
But he was expelled after donating to the UK Independence Party, which wants Britain to leave the EU.
Mr Wheeler also said he would be voting for UKIP in the upcoming European elections in June.
He told the BBC: "Their (UKIP's) position is far nearer to what I would like to happen than anybody else's.
"I do want the Conservatives, if they are in power, to try very hard to get the European Union to accept a much looser relationship and to put us back into a position more or less where we were when we first joined - a wonderful trading relationship but not much else.
"I think they should try to do that, but more than likely they will fail and then we would have to get out."
'Not let matters rest'
Before Britain signed up to the Lisbon treaty in December 2007, the Conservatives promised a referendum on the grounds that it reduced the UK's ability to make decisions independent of Europe.
But, said Mr Wheeler, the Tories had now dropped that pledge if the EU Treaty had been ratified across Europe and was already in force before they came to power.
He said their current promise that they "would not let matters rest" regarding the treaty - if it was already in force - was not sufficient for him.
He said that they should still hold a referendum and then use the result - which he predicted would be "no" to the treaty - in negotiations with the EU.
The decision to expel Mr Wheeler is expected to be formally announced by party chairman Eric Pickles after a meeting of the Conservative Party board.
As a precursor to expulsion he has been formally suspended and has 28 days in which to appeal. Mr Wheeler indicated that he would not do so and said he would not apply to rejoin the party in the future.
Nigel Farage, UKIP leader, said: "I'm thrilled that Stuart Wheeler has decided to support our vital campaign. The decision of who rules Britain is vastly more important than any traditional tribal loyalty."