Immigration will be the main factor pushing up the UK's population over coming years, a new report has found.

Right-wing group Migrationwatch claimed that immigration will account for 85 per cent  of the UK's population growth over the next three decades.

The report says that immigration made up 60 per cent of the increase in population seen in the five years to 2002.

The findings will fuel the debate over migration into the UK - which has intensified since EU expansion earlier this month.

"These statistics highlight just how large the scale of immigration into the UK has become in a few short years," said Sir Andrew Green.

"It has taken place without - until very recently - any discussion or explanation of the wisdom of, or rationale behind, such a large influx in such a short time."

Sir Andrew went on to call for a "top to bottom" review of the immigration system and is demanding to know whether ministers believe the increase in population is necessary.

"The increased scale of immigration over just five years has been remarkable. It has already more than doubled and we have yet to see what effect the enlargement of the EU might have," he added.