The Conservatives have unveiled what they say is a new strategy for managing immigration to the UK -how does it differ from the government and their own previous policy?
The Tories say immigration is an issue which cannot be ducked
What are the Conservatives saying on immigration?
The basic policy is that the Conservatives say they welcome economic migration where it benefits Britain - but at the same time believe we must devise limits because of the impact on public services, the environment and "community cohesion".
In other words, the party believes that Britain benefits from migration, but "not all or any migration".
So what's the detail?
The policy makes a distinction between economic migration and asylum seekers and refugees. The party's pamphlet, co-authored by David Davis and Damian Green, the party's shadow home affairs and immigration spokesmen, then focuses on economic migration. It envisages a two-stage process.
First, decide who should be eligible to come and work in Britain.
Second, set limits to control numbers in the interests of wider society
The policy would not stop immigration in "most years", says the party, but it insists the numbers would be lower than at present.
How does this differ from the party's previous position?
At the 2005 general election, former party leader Michael Howard proposed an annual limit on immigration with, most controversially, a quota for refugees. While the asylum proposals have been dropped, the idea of an annually-set limit remains in place.
How does the policy differ from the government?
The government is rolling out a points-based migration system, similar to systems judged to be a success in similarly successful economies.
In short, the system allocates points for skills. The more skills, the more points and the more likely an immigrant will be allowed in and, if they want to, settle.
This system does not apply to European Union citizens who already have complete freedom of movement. Separate restrictions will apply to Romanian and Bulgarian workers whose countries soon join the EU.
The points system will be monitored and adjusted with the help of a special Migration Advisory Committee. It will advise ministers on skills shortages in the British economy.
But are the Conservatives talking more about social factors?
The Conservatives claim concern about community cohesion is what is lacking from government policy.
The Tories say immigration policy should take into account the over-all competitiveness of British-born workers, the capacity of public services and the environmental impact of a rising population.
This plays into the heart of the current debate where, in the wake of significant arrivals of Eastern European workers, there are concerns about the ability of some areas to offer enough school places or decent housing.
How does the government respond?
Home Secretary John Reid says that concerns for community cohesion are in fact right at the heart of his agenda. The plans for the Migration Advisory Committee focus on economic advice.
But policy papers also talk about working out how to manage migration for the country's wider benefit, including balancing economic demand with pressures on social cohesion. We won't know how this will work in practice until the advisory body is established which will be at the earliest next spring.
Is there evidence for fears over public service pressure?
It's very difficult to calculate accurately. Young workers from Eastern Europe tend not to cost anything - they come to work and pay taxes, taking very little out. But if they then settle with a family, the equation may change.
Slough has become a touchstone in this debate, having been used as example of leaps in the number of foreign children in local schools and associated increased demand for housing.
Special budgets exist to help children settle in schools - but if there are not enough specialist teachers available, then that process takes a lot longer.
So depending on your interpretation of how society and policy works, pressure on public services may come down to poor local authority planning, central government's funding strategy, the immigration system itself or the free market in labour.
What about the impact on British workers?
Again, this is a highly contentious area of debate and the experience depends on different parts of the economy.
In construction or the hospitality industry, there is ample evidence that Eastern European workers have tended to plug holes.
But fears have been mounting over competition for jobs among the poorest in society.
Some economists argue the affluent gain most from immigration because it lowers the costs of the services they use most.
At the same time MPs from all parties now appear concerned about the potential for tensions in communities if local people are priced out by migrant workers accepting lower wages.