Islam, it is often assumed, by Muslims and non-Muslims alike, is a missionary faith.

It isn't.

Yes, the Quran does of course encourage the believers to spread God's word: "Invite to the way of your Lord with wisdom and good instruction, and argue with them in a way that is best." But it also recognizes religious, cultural and ethnic diversity: "O mankind, indeed We have created you from male and female and made you peoples and tribes that you may know one another." How can Muslims presume to convert to everyone to Islam when God Himself, in His infinite wisdom, chose not to? "And if Allah willed, He could have made them [of] one religion, but He admits whom He wills into His mercy." In fact, the Quran tells Muhammad, at one stage, to adopt an "agree to disagree" approach to the non-believers: "For you is your religion, and for me is my religion."

In a diverse, globalised world, which depends upon religious tolerance and harmonious relations between communities, Muslims have to learn to live together with non-Muslims without surrendering to the "I must convert all the kafirs" itch. There is no need for an Islamic equivalent of the Jehovah's Witnesses.

So it frustrates me when many of my co-religionists get excited at the prospect of people converting to Islam, especially celebrities. Does it matter if Michael Jackson was on the verge of a deathbed conversion to Islam? Should we encourage Simon Cowell to become a Muslim? (No and no.)

Faith is being reduced to a numbers game. "Islam is the fastest-growing religion on earth," is the mantra that my Muslim friends recite with glee. So? I've never quite understood how adding to the world's burgeoning Muslim population helps me, the Islamic world or the faith itself. We have enough theological, political, cultural and socio-economic problems as it is, without mindlessly adding to our numbers. I can't help but sympathise with the senior Indian Muslim cleric who once revealed to me his (private) advice to Hindus considering converting: "Don't bother. Not until we Muslims get our house in order."

These days, it is converts themselves who often damage the Islamic cause. The majority, of course, are peaceful, law-abiding citizens whose conversions have enriched their lives and those of the Muslim communities into which they have been welcomed. But what about men of violence like Richard Reid, Germaine Lindsay and Dhiren Barot? Others that the "ummah" could have done without include Adam Gadahn, Al Qaeda's media spokesman and Colleen La Rose, aka "Jihad Jane".

Then there is the thorny issue of Islam's apostasy laws, which prevent Muslims from converting to other religions. We cannot expect to "compete" with other faiths for new recruits if those faiths aren't given a similar opportunity to try and recruit from inside the Islamic world. In Kuwait, in 1996, amid a row over the conversion of a businessman to Christianity, one cleric argued: "We always remind those who want to convert to Islam that they enter through a door but that there is no way out." This is as illogical as it is unIslamic. How can you expect people not to change their minds? Or dare deny them that freedom?

Above all else, religion should not be about competition, which is for bankers and financiers, not for the faithful. The idea that there should be a marketplace of religions in which priests, imams, rabbis and pandits jostle with each other to sign up new believers is deeply divisive. The only "invisible hand" in the world of the religious should be God's.

If there is to be mutual respect between religious communities, and much-needed inter-faith dialogue, there can be no hidden agendas. Muslims, Christians, Jews and the rest should never go into discussions or debates with the secret aim of trying to convert one another. Nothing could be more counter-productive or damaging to relations between the faiths. For Muslims, in particular, accused by the far right and sections of the liberal left, of trying to "Islamize" Britain, and Europe, it also makes tactical sense to avoid feeding this false narrative.

We are not missionaries. The role of a Muslim is not to convert the rest of the world to Islam. We should instead focus on becoming the best possible Muslims, and leading the best possible lives, that we can. If the rest of the world then chooses to follow our lead, so much the better.