Clacton MP Douglas Carswell, one of the more vocal eurosceptic backbenchers who has had cross words with the prime minister in the past, told The Huffington Post UK it was a "magnificent speech" and the the party was now united.
"It's truly historic because it accepts the need for an in or out referendum," he said.
Carswell also said Cameron's decision to promise a referendum put Labour in an extremely difficult position.
"I've always been genuinely baffled why the party of Keir Hardy, the party that stood for the ordinary working man, wasn't in favour of giving people a referendum on the subject, the pressure will be on Miliband," he said.
"If Labour makes the mistake of going into next election opposting a referendum, Miliband could be in line to be the next Kinnock."
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Fellow eurosceptic Mark Pritchard said the speech "settles the issue" of Europe for the Conservative Party.
"Credit where it’s due, David Cameron is the first British prime minister in nearly four decades to offer the British people a referendum," he said.
"I think questions now arise about the other mainstream political parties, particularly the Labour party. I think probably by 2015 the Labour party will have inserted within their own manifesto some sort of referendum commitment as well. So the problems on Europe have now transferred from the Conservative party to Ed Miliband’s party."
Richard Ottaway, the Tory chairman of the Commons foreign affairs committee who is in favour of continued EU membership, told the BBC that Cameron had given a speech that would be listend to right acorrs the capitals of Europe.
"He is the first national leader inside Europe to say actually, we can't go on like this, we have to change. This is real leadership going on here," Ottaway said. "He is showing leadership, leadership to this country and leadership to his Europe as well."
And South Northamptonshire MP Andrea Leadsom, the chair of the Fresh Start group of Tory MPs who want a "new settlement" with the EU said the prime minister's plan to renegotiate Britain's relationship was not about "cherry picking" or "getting a special deal for ourselves".
"I think what the prime minister has in mind is some changes at EU level that reflect the fact that there will be those countries moving towards greater integration as they share a currency, and a whole raft of countries - 10 of them who are not euro member states - who need to have a different a more flexible relationship so he's quite clear this isn't about us trying to wriggle out of things here and there, this is about a whole new settlement."
However Lord Ashcroft, the former deputy chairman of the party and major donor, said it was "time for Tory eurosceptics to declare victory and talk about something else".
"For most voters, including those who will need to vote Conservative for the first time if we are to have any hope of a majority, Europe barely registers on their list of concerns.
"The principal benefit of our referendum policy is not that it gives our campaign a headline; it is that it allows us to put the issue to rest and move the conversation on to what the voters want to discuss.
He added: "Tories must remember that we can only get what we want once we win an election. The more we talk about changing our relationship with Europe, the less likely it is to happen."