Image caption Mr Fox said he did not doubt the sincerity of proponents of same-sex marriage

The government's plan to legislate for same-sex marriages is "divisive, ill thought through and constitutionally wrong," former Defence Secretary Liam Fox has said.

In a letter to constituents, Mr Fox said same-sex relationships should be treated "with tolerance and respect".

But there did not appear to be "much demand" for the change, he said.

The government has said that the measure will strengthen the "vital" institution of marriage.

"The legislation looks as though it was made on the hoof to deal with the political problem du jour", Mr Fox wrote.

It would put the Church of England in an "anomalous and absurd" position by banning it from carrying out same-sex marriages, he added.

"If the 'exemption' is, as stated, because the Church had made clear their objection to same-sex marriage then why not exempt the Catholic Church which has been even clearer in its opposition," he said.

'Vibrant'

"The idea of making certain practices illegal for one Christian Church, but not others, risks further weakening and splintering Britain's traditional religion at a time when many Christians feel that they are under threat on a number of secular, political and cultural fronts.

"To fail to understand this is to risk an affront to a large stabilising and normally acquiescent section of this country which will sow completely unnecessary seeds of dissent."

The anomaly could lead to legal challenges, Mr Fox warned.

"We should not be intruding on the freedom of worship that is the proper preserve of the Churches not the courts," he said.

The move would enjoy greater public support if it were "simply an argument about righting a wrong", Mr Fox said.

Instead, it "smacks of a form of social engineering of which Conservatives should be instinctively wary".

Advocating the change in December, Culture Secretary Maria Miller argued that "extending marriage to same-sex couples will strengthen, not weaken, that vital institution".

"I have been absolutely clear that I would never introduce a bill that encroaches or threatens religious freedoms," she told MPs.

"I believe the proposals strike the right balance - protecting important religious freedoms while ensuring that same-sex couples have the same freedom to marry as opposite-sex couples.

"By making marriage available to everyone, we will ensure that it remains a vibrant institution."