Campaign group Migrationwatch has given its backing to Conservative immigration policy but has called for more specific policy commitments.

Publishing a report on the main parties' asylum and immigration plans the group calls on voters to look beyond the manifesto rhetoric.

The report says that all the party manifestos are designed to sound tough on immigration but warns "they have to be examined carefully" against the track record of the party.

The report also claims that ministers have "actively encouraged" economic immigration - revealing a "substantial increase" in the number of spouses admitted.

The study concludes that asylum is now less than 20 per cent of total foreign immigration.

"There are some similarities, probably deliberate, such as the Labour and Liberal Democrat adoption of a 'points' system, for work permits. But the fundamental issue remains overall scale," said Migrationwatch chairman Sir Andrew Green.

"Here - contrary to what some commentators have tried to suggest - the main parties are far apart. Immigration under this government has tripled – despite hardly a mention in their last two manifestos."

Sir Andrew also calls for greater clarity from the Tories.

"The Conservatives have said that they would make a substantial reduction in immigration, in contrast to Labour, but they have not been specific," he added.

"Poll after poll shows that a large majority believe that immigration should be reduced – but, so far, their views have been ignored.

"Tough sounding talk is no substitute for a firm limit. That will not be easy to achieve but it must be the declared goal if public concern is to be eased."