Skipton MP David Curry defied his party by voting for a second reading of the EU treaty, saying it had always been his "desire" to see engagement with Europe.
The EU reform treaty cleared its first Commons hurdle this week after a five-hour debate, thereby kick-starting at least 15 days of debate over the coming weeks.
The Tory MP, right, said: "It is always a difficult matter to find oneself in a small minority on an issue that engages one's party with a great deal of passion.
"I suppose if I look back on what has really animated my political life, it has been the desire to see the UK engage thoroughly with Europe.
"Too often, the treaty is treated as a religion. The European Union is not a religious issue but a political one."
Mr Curry told MPs he would support the treaty but not vote for a referendum when the time came.
He said: "It will be with great sadness, because of the position of my party, but with the understanding that tolerance of views has always been understood in this House, that I shall vote the way I feel I must. I hope I may yet see the UK deciding we should get stuck in to Europe."
A total of 19 Labour MPs voted against the Bill's second reading, including Batley and Spen MP Mike Wood. A motion to approve the bill in principle won by 362 votes to 224.
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