Lib Dem leader Nick Clegg has defended his handling of the EU treaty vote, after 15 of his MPs chose to defy him.
Mr Clegg ordered his MPs to abstain from the Commons vote
He said there had been "a few folks who didn't agree" with his order to abstain, but it would not affect the party's "unity and sense of optimism".
Shadow Commons leader Theresa May said earlier he had "flunked his first big test" as party leader.
The Tories, who called the vote for a referendum on the treaty, will try again when debate reaches the Lords.
Mr Clegg, who has been Liberal Democrat leader for less than three months, ordered his MPs to abstain from a vote on the Tory amendment, calling for a referendum on the Lisbon Treaty.
Almost a quarter of all Lib Dem MPs, including three frontbenchers who resigned from their positions, defied him to vote in favour of it.
Speaking on a visit to Oldham earlier, Mr Clegg said: "It's part of leadership. It's a difficult issue. It doesn't in any way affect the unity and sense of optimism in the party.
"It's my job as a leader to make sure that people are as united as possible. There were a few folks who didn't agree, that's the way these things happen."
He said "as the dust settles" people would see the Lib Dems had been "very consistent" in their view that the "real question" to be put to a referendum was Britain's long-term EU membership.
All three of the main parties promised a referendum on the EU Constitution in their 2005 manifestos.
But the constitution was abandoned and the Lib Dems and the government argue the treaty is different - so it does not require a referendum.
The Tories, along with some Labour and Lib Dem MPs, the UK Independence Party and others, say it is essentially the same thing and accuse the other parties of breaking a promise.
In all 15 Lib Dems and 29 Labour MPs defied their party leadership to back the Tory amendment. Three Conservatives voted against their party to oppose a referendum.
Lib Dem home affairs spokesman Chris Huhne, who narrowly lost out to Mr Clegg for the Lib Dem leadership, denied suggestions his leader had created difficulties for himself.
He told the BBC: "I don't recognise the description of this as kamikaze politics at all.
"It seems to me that we have had - as all the parties have had - a difference of opinion over an interpretation of whether or not the Lisbon Treaty is sufficiently close to the old constitutional treaty to justify a referendum on that."
'Heart and soul'
MEP Chris Davies said Mr Clegg had had "a very difficult set of cards to play" but added he was "so absolutely determined to fight the liberal corner, even when his views may not be popular, that he is at one with the very heart and soul of this party".
But the Lib Dems came under attack in the Commons, where shadow Commons leader Theresa May said Mr Clegg had "flunked his first big test" as leader.
"He sat on the fence as a point of principle, he divided his party after only a few weeks and he's created two classes of frontbenchers, those who have to resign for rebelling and those who don't."
The Conservatives have vowed to introduce their amendment calling for a referendum when the EU (Amendment) Bill - which would ratify the treaty - goes to the House of Lords.
The amendment was defeated in the Commons on Wednesday night, by a majority of 63, but exposed divisions in all three parties - particularly the pro-European Liberal Democrats.
Shadow foreign secretary William Hague said the Lib Dems could still help secure a referendum on the treaty if they abstained again in the Lords, where the government has no overall majority.
"The Liberal Democrats' position will once again be pivotal. We will see if they follow their three-line whip in the Commons to abstain," he said.
The result of yesterday's vote means Parliament itself will decide to ratify the treaty, signed by EU leaders last December.
All EU parliaments must ratify the treaty before it can come into force. The only country which has committed to a referendum is Ireland.