Liberal Democrat MP Sarah Teather says voting against the Marriage (Same Sex Couples) Bill in February was “an extremely difficult choice”.

In an interview with the Catholic Herald, the north London Brent MP and former children’s minister said: “In many ways I’d rather not resurrect the whole argument again. It wasn’t one of those issues that I went into politics to tackle, but once a vote became inevitable I spent ten or 11 months weighing up the issues – of equality on the one hand and family life and what it meant for the definition of marriage on the other.”

She added: “I did a lot of reading and eventually I came to my conclusion, based not on any effect it would have in the short-term, but on the change it would mean for marriage over a longer period of time.”

Ms Teather was among four Lib Dem MPs to vote against the bill in its second reading – along with Sir Alan Beith, Gordon Birtwistle and John Pugh.

Seven other Lib Dem MPs were also absent from the vote.

Asked if she was tempted to abstain, Ms Teather replied: “No, because I had thought very hard about it, and finally reached a position, so to try and dodge expressing a view didn’t feel right.”

Directly after the second reading vote of the Marriage (Same Sex Couples) Bill on 5 February, Ms Teather wrote on her blog: “This evening I voted against the second reading of the same-sex marriage bill. It was one of the most difficult decisions I have ever taken. As a life-long liberal and a committed Catholic I spent many months reflecting on this issue in the lead up to the vote.”

She added: “I have found this a difficult decision because of my work previously on gay rights issues, and my judgement is finely balanced. I recognise that others may reflect deeply on these issues and come to a different view, in good faith. But it is my view that where the extra protections offered to same-sex couples are marginal, and where the potential negatives to society over a period of time may be more considerable, I am unable to support the bill.”

The House of Commons will debate the bill as part of its third reading on Monday 20 May and Tuesday 21 May.