Inward migration to the UK has reached "two million every decade and probably more", a think tank has claimed.

Migrationwatch UK warns that immigration "is now running at double the rate of a decade ago and the trend is relentlessly upwards".

Chairman of the organisation and former diplomat, Sir Andrew Green, says that 250,000 migrants are now entering the UK every year.

"Our latest analysis of all the available figures...shows that, even using very cautious estimates for illegal immigration we are approaching a quarter of a million migrants a year for the first time in our history," he said.

The anti-immigration pressure group is concerned that 95 per cent of migrants are not genuine refugees.

And unless the government acts, predicts Green, the system will be thrown into disrepute.

"Continued failure to get a grip of this situation will play into the hands of the far right who seek to exploit the situation for their own ends and to whom we are totally opposed," he cautions.

"Immigration at this rate will have a profound effect on the nature and shape of our society for decades to come.

"It is therefore essential that this subject be brought out of the closet so that there can be an open debate based on the facts."

Migrationwatch UK is concerned that "many of the arguments adduced in favour of the current large-scale immigration are unsound either in fact or in economics, or both".

"We start from the belief that the scale of net inward migration is now so great as to be contrary to the interests of all sections of our community," it argues.

Green became alerted to immigration issues while "the foreign secretary's principal adviser on the Middle East in the mid '90s".

"At that time he spent two years trying, on the prime minister instructions, to remove Islamic extremists from Britain but was frustrated by the British courts," explains the group's website.

"On retirement he was able to look into matters further...[and] he decided that this was a matter which should be brought to public attention and so founded Migrationwatch UK towards the end of 2001."