WE are a nation of immigrants. For millennia, people of different origins, races and beliefs have been coming to these shores. Some came by choice, some by need. Not all had a formal invitation. In general they've brought new skills and ideas that have enriched everyone's lives. They've made us what we are today - a multi-cultural society.

Only a few idiots want to reverse that process. But it's clear that the growing diversity of society creates tensions as well as opportunities. The comments of Cambridgeshire Chief Constable Julie Spence can't be dismissed as special pleading from a cash-strapped copper. Her remarks about the impact of immigration on crime, public services and the social fabric struck a chord everywhere.

Immigration and the integration of people with different creeds, culture and values, whether they're here by choice as migrant workers or by need as asylum seekers, is the greatest challenge that society faces today.

I don't blame anyone for wanting to come and live in the UK. It is a land of opportunity. Migrants contribute a lot. They do the hard, badly-paid work that their hosts turn their noses up at; or they create new industries - like generations of successful Asian business people.

But, when the person in the street hears that 680,000 people from eastern Europe have applied to work in Britain and that we also have 450,000 failed asylum seekers in residence, they don't reach for a calculator and work out that this is still a small percentage of our total population.

When they hear this is putting services under pressure they don't remember that the local hospital would close tomorrow without overseas staff.

Finally, when the person in the street hears that a tiny minority from migrant communities is involved in serious crimes involving drugs, knives and people trafficking, they don't look in their history books and see that the same thing was said of previous immigrants, often on the flimsiest of evidence.

Quite frankly, they get very worried and, in that worried state, become easy meat for the idiot extremists I mentioned earlier. That is a serious threat to a tolerant, just and healthy society.

What's needed first in this overheated debate is clarity. That is why it's good news that the Migration Impacts Forum set up by the Government is going to analyse the effect migration has had on public services and community cohesion. It is vital that solutions are based on evidence, not hearsay.

Secondly, what's needed is cash: for the front line services, schools, health providers and councils that cope with the challenges caused by migration.

Thirdly, what is needed most of all is confidence in a system that is fair but firm.

Genuine victims of persecution have a basic human right to safety and asylum in the UK. Equally, migrant workers who are here legally should enjoy access to services and amenities.

However, that must be balanced by support for the Border and Immigration Agency to develop robust procedures to detect and deter illegal entry to the UK. There must be a sensible solution to the problem of illegal migrants already here. The amnesty proposed by a Lib Dem leadership hopeful this week is not the answer. But neither is expecting that they will pack their bags and go home on the next plane.

Finally, what is needed most of all is mutual respect between newcomers and their hosts. With that respect must come an understanding that our tolerance does not stretch to anti-social behaviour or crime.

Immigration has enriched this country because most people realised it would involve them embracing new values and experiences while still retaining important elements of their own culture and identity. That involved everyone being willing to make sometimes painful adjustments to their established attitudes and customs. It is time that everyone showed willing again.