Concern: Sir Andrew Green believes immigration is an issue that the main parties must address ahead of the General Election

It is now 14 years since I co-founded Migrationwatch with Professor David Coleman of Oxford University. In the early years we had to face snide accusations of racism, notably from the BBC. Our aim was simply to get the facts about immigration properly understood and to have a sensible debate about the issues it raised.

We have now won that debate in the court of public opinion.

Poll after poll has shown that immigration is right up there with the economy as an issue of national concern. The polls also show that nearly 75 per cent wish to see a reduction in immigration, including 50 per cent who want to see it reduced ‘by a lot’. This broad view is shared by members of the ethnic communities, among whom a majority wish to see a reduction.

Sadly, Thursday’s immigration figures will have been a huge disappointment to the public. For the year ending last September, net migration reached nearly 300,000. This is three times the Government’s target, and 50,000 higher than the level when the Government came to office.

Despite the clear and long-standing evidence of the strength of public opinion, some are today arguing that, instead of policies to reduce immigration, the objective should be to mitigate its impact. The clear implication, of course, is that since nothing can be done to control immigration, we might as well get used to it.

The public will simply not accept that position. They will be perfectly happy with controlled immigration at a sensible level.

They recognise its benefits in an open economy and society. The problem is one of scale and they realise that the implications of net migration on the present scale are breathtaking.

If this is allowed to continue, we will have to build the equivalent of three cities the size of Birmingham in the next five years. This is clearly impossible, so the effect will be even more overcrowding and congestion, particularly in our cities.

Worse, in just eight years the UK population would reach 70 million, and 80 million in 25 years and still climbing. The sooner we get a grip, the better.

Apart from the impossibility of building infrastructure on such a scale, our public services are coming under increasing strain. This has practical consequences. A neighbour of mine who was checking in to her local GP’s surgery had to tap the screen to choose a language. The top option was not even English – it was Polish.

The metropolitan elite who are so keen on immigration may well have health insurance but, for those sitting in the queue, it is altogether different.

No less important is our social cohesion. We already face a situation in which immigrant children in our cities find themselves in schools with virtually no UK-born children. Indeed, net foreign migration since 1998 comes to a total of more than four million. How can we possibly achieve integration at such a pace?

We now face what might amount to a conspiracy of silence. The three main parties all have good reasons to avoid immigration during the coming Election campaign.

The Conservatives, despite genuine efforts and support from the top when it was needed, have not succeeded in getting the numbers down. Labour know that it was under their watch that immigration first spun out of control. In 1997, net migration was a mere 48,000. This trebled in a couple of years before reaching a peak of 320,000 in 2005.

Impossible: If net migration continues at its current pace, the UK will have to build the equivalent of three cities the size of Birmingham in the next five years

They clearly had a deliberate policy of increasing immigration, but failed to mention it in their three manifestos during that period. Furthermore, the policies they are suggesting now will have no significant impact on numbers – an aspect which they decline even to discuss.

As for the Liberal Democrats, they have never believed in reducing immigration and, in Coalition government, they have done their best to hamper attempts to limit it.

Any such outcome would be reinforced by BBC home affairs editors and producers – many of whom are only too happy to avoid the subject, and especially any serious treatment of the case against mass immigration, whenever they can. This leaves the puzzle as to how immigration could have increased so rapidly in the face of the Government’s commitments.

We'll need three more cities the size of Birmingham Sir Andrew Green on immigration

There were two main factors. Economic migrants from outside the EU increased significantly, and migrants from the EU itself doubled in the past two years.

The Government is trying to spin this as ‘a problem of success’. The Treasury has long favoured high immigration because it gives the impression that the economy is growing that much faster.

However, what really matters is not the size of the economy but wealth per head. All the evidence is that the impact of immigration on this key measure is extremely small. Nor is there any benefit to the national budget.

If you choose a particular group of immigrants over a particular period, you can get a positive result, but even immigration enthusiasts have had to admit that the budgetary cost of all immigration since 1997 has been somewhere between £115 billion and £160 billion.

It cannot possibly be the case that, on a small island, we are really unable to control our borders. So what can be done?

There is no need for yet more laws. The present rules need to be implemented more effectively with close attention paid to each route of entry and, crucially, to departures.

The first step must be to restore exit checks as people leave Britain. Incredible though it may seem, these have not been in operation for 20 years. As a result, the Government has no idea whatsoever who is on this island. Exit controls, due at last to come into effect next May, will make a start on that.

Correct approach: Ukip will certainly gain from a public mood of disillusionment, amounting to anger, at the failure of successive governments to heed their views on immigration

For example, non-EU students are a major concern. Despite a barrage of propaganda from the education sector, the fact is that they have been arriving at the rate of about 150,000 a year, but only 50,000 a year are leaving.

Exit checks will tell us who has not left, but those who overstay still have to be located and removed – a huge task which is pathetically under-resourced.

Fewer than 5,000 immigration offenders are being removed every year compared to an illegal immigrant population that could well be as many as one million.

A major increase in resources is therefore needed. At present only one quarter of one per cent of Government expenditure goes to immigration control.

We have called for this to be doubled. Serious issues call for serious funds.

As for EU migrants, we have the promise of a negotiation to reduce their access to benefits.

It remains to be seen whether this will have much effect.

There may well have to be a much tougher negotiation with our partners.

In the meantime, Ukip must have been smiling all the way to their spring conference. Unfortunately, their prospects of ensuring any effective action are very slim. Nevertheless, they will certainly gain from a public mood of disillusionment, amounting to anger, at the failure of successive governments to heed their views on immigration.