Lincoln’s Conservative MP has defended his views on marriage equality after telling a constituent the move could lead to polygamy and child marriages.

Karl McCartney had responded to an email asking him to support equal marriage for gay couples by telling his constituent that while he welcomed “changes made and achieved by the LGBT community in recent decades”, the community had “exhausted” the equal rights cause.

He criticised the argument, which was made in an email drafted by the British Humanist Association, saying that it was not “advocating multi-partnership marriages, nor a reduction in the age of permitted marriage. But if one takes your ‘arguments’ to any conclusion that is where we could end up.”

The BHA told PinkNews.co.uk Mr McCartney’s assertion “seems not to understand” the argument.

Mr McCartney has since told the Lincolnshire Echo he believes “a religious marriage is one between an individual man and individual woman”.

He said: “I strongly feel that society is made stronger by people’s commitment to one another and when we make vows to each other.

“I also support the commitment and love between individuals, regardless of their sex or gender, and feel that it should be encouraged, supported and celebrated. I believe civil partnerships do this.

“I do, however, firmly believe that no institution should be forced to perform a ‘same-sex marriage’ against the will of that institution, whether it be a religious one or otherwise.

“Marriage, in my belief, is widely seen as a religious union and I will always support my long-held Christian and mainstream views on this matter.”

The government’s proposals would allow gay couples to marry in civil ceremonies but not religious ones and it has told opponents that churches would not be obliged or even allowed to perform marriage ceremonies for gay couples.

Liberal and Reform Judaism, the Quakers and the Unitarians have all voiced their support for the ability to hold religious gay marriages, however.

A prospective parliamentary candidate for the Lincoln Labour Party criticised Mr McCartney’s correspondence with his constituent.

Lucy Rigby said: “I thought Karl’s letter was offensive, wrong and, to be frank, quite bizarre.

“When you receive a letter like that as a constituent, Karl reveals himself to be a holder of some pretty odd views and, to put it in context, he’s even contradicted by his own party.

“People in Lincoln want a sensible and intelligent MP that gets stuff done – they don’t want an extremist with these fringe views.”

Mr McCartney told the Lincolnshire Echo: “I, for one, hold the freedom of speech very dear. A principle my political opponents clearly do not and, in failing to do so, I am saddened that they have chosen to subject me and those dear to me to a torrent of abuse. […]

“The Labour Party in Lincoln have now stated that they believe there should be gay religious marriages and that anyone who does not hold that similar view to them is an extremist.

“I would imagine that many people of all faiths, and indeed those of none, in Lincoln and Lincolnshire will take offence at the suggestion that those who oppose the redefinition of marriage are extremists with fringe views.

“While I am aware that a number of people disagree with me, it is clear from both my postbag and the Coalition 4 Marriage petition available at c4m.org.uk , which over 460,00 people have now signed, that a significant body of opinion in our city and up-and-down our country share my views.”

PinkNews.co.uk this week revealed that the Catholic Education Service had asked nearly 400 state schools across the country to “draw attention to” the anti-marriage equality petition among students, with one school in London giving a presentation ending with the words “Sign the petition” to schoolchildren as young as 11.