Iain Duncan Smith is the first leader of the Conservative Party to have been elected by members of the whole party, not just the MPs.

He has a mandate to lead the party through the next general election - and all of us owe him the loyalty due to our leader.

Much as I regretted the imposition of a three-line whip, however soft, this historic vote had nothing to do with a challenge to IDS

After all, we need political parties to make democracy work.

The British party system has served us well and is infinitely preferable to the corrupt system of patronage and sale of votes which sustained governments until the Great Reform Act of 1834 - and I speak as the member for one of the original constituencies who sent their man to the parliament of 1265, and which now includes the "rotten borough" of Old Sarum.

After winning the Bristol Election of 1774, that great English statesman Edmund Burke delivered an address which established the principle still cherished by MPs of all parties: that they are representatives, not delegates.

Principle

He said, "Your representative owes you, not his industry only, but his judgment; and he betrays, instead of serving you, if he sacrifices it to your opinion".

This principle still rings true - and is ignored by party managers at their peril.

The only parliamentary vote Margaret Thatcher lost in her 11 years as prime minister was on the issue of Sunday Trading - both a moral and religious issue. I abstained on that vote, just as I abstained on the proposed amendment to the Adoption Bill on 4 November.

We are not a European-style Christian Democrat Party with party lines on moral and religious issues

I made my judgment having listened to the representations of respected charities such as Barnardos and the NSPCC (and my wife serves on their local Committee in Salisbury) but also having been briefed by those professionals in my constituency whose job it is to place children for adoption and fostering.

I listened to the cases of real children in real trouble. I listened to the consequences of excluding certain categories of adults from the opportunity to cherish those children in a loving home.

The rights of adults, gay or otherwise, played no part in my decision. Nor did the "lies, damned lies and statistics" with which I am so familiar as a former teacher of economics.

Hopes

Above all, much as I regretted the imposition of a three-line whip, however soft, this historic vote had nothing to do with a challenge to the right of IDS to lead the Conservative Party.

I want him to succeed. I want a Conservative government.

But I also want it to be quite clear that we are not a European-style Christian Democrat Party with party lines on moral and religious issues; nor are we a US-style Republican Party with deep dependence on some branches of Christianity.

The Conservative Party is a secular party. And I am a Christian who on issues such as adoption will exercise my judgment, not sacrifice it to someone else's opinion.

Robert Key is shadow minister for international development