Until recently immigration was regarded as a no-go area for politicians. Michael Howard, the former Tory leader, was accused of “dog whistle politics” in focusing on it in the 2005 election. In the 40 years since Enoch Powell proved immigration was political dynamite, the mainstream proceeded with care.

That is changing. Britain has been transformed as a result of large-scale immigration. The influx that began in the mid1990s was not just about Polish plumbers. Most new immigrants in recent years have been from outside the European Union. Britain has been drawing in people from all over the world.

Mostly this has been good, as we have long argued. Each new wave of immigrants has brought dynamism to the economy. Those with entrepreneurial energy have created businesses and in some cases entire industries. They have filled gaps in the workforce by taking jobs that home-grown workers cannot or will not do. The City of London could not prosper without its pool of multinational labour and neither could other parts of the economy.

Yet there has to be a balance. Official projections show that our population will grow by the equivalent of seven Birminghams by 2031. The European commission projects that the population will rise from nearly 61m now to 77m in 50 years’ time. These small islands will become the most populous country in Europe, mostly due to the effects of immigration.

The difficulty has been in framing a policy that answers concerns about overpopulation, cultural isolation and pressure on space and resources. It must also not pander to xenophobia and not deprive business of workers. The government’s points-based system, introduced this year, borrowed from the Australian model but without an annual cap.

Now an all-party group of MPs, led by Frank Field, the former Labour minister, and advised by Migrationwatch, the pressure group, has an alternative. It would allow a free flow of economic migrants to Britain each year, using the points-based system, but limit the time that such workers could stay to four years. The aim is to break the link between economic migration and permanent settlement, with the latter capped to perhaps 20,000 a year.

Mr Field brings weight and respectability to this debate. His “balanced migration” blueprint may not be perfect but it is more flexible than a crude cap and appears to steer a neat line between Britain’s economic needs and the social pressures arising from too rapid an increase in population. The debate he is trying to start is too important to ignore or to be swept under the carpet by ministers.