Labour ministers deliberately encouraged mass immigration to diversify Britain over the past decade, a former Downing Street adviser has claimed.

Andrew Neather said the mass influx of migrant workers seen in recent years was not the result of a mistake or miscalculation but rather a policy the party preferred not to reveal to its core voters.

He said the strategy was intended to fill gaps in the labour market and make the UK more multicultural, at the same time as scoring political points against the Opposition.

Mr Neather worked as a speechwriter for Tony Blair and in the Home Office for Jack Straw and David Blunkett.

Tony Blair wanted mass migration

"Mass migration was the way that the Government was going to make the UK truly multicultural," he wrote in in the London Evening Standard.

"I remember coming away from some discussions with the clear sense that the policy was intended - even if it wasn't its main purpose - to rub the Right's nose in diversity and render their arguments out of date."

On the BBC's Question Time programme, Jack Straw faced questions about whether the policy has played a part in the rise in popularity of the BNP.

"The British public are aghast at the display of bias from the BBC, the venom from the political class, and the sheer unfairness. That was not a genuine Question Time."- Nick Griffin on his appearance on the BBC show.

Mr Neather dismisses that argument, saying the policy has "enriched" the UK and made London a more attractive and diverse city.

Critics have been quick to accuse the government of creating an "immigration conspiracy" and introduced mass immigration to Britain for "cynical" political reasons.

Sir Andrew Green, chairman of think tank Migrationwatch UK, said: "Many have long suspected that mass immigration under Labour was not a cock-up but also a conspiracy, they were right."

Liberal Democrat home affairs spokesman Chris Huhne said: "If this is true it is deeply shocking that the Government can have taken such significant decisions without public debate and public consultation.

"The essence of good decision-making in a democracy seems to have been ignored.

"Legal migration has undoubtedly brought great benefits to this country by attracting skills and talents from all over the world, but the shambolic control of our borders over the last 10 years has left a legacy of illegal migration which creates social tensions."