Under the Australian system, migrants are only granted skilled migration visas if they pass a points test based on what type of job they do, their age, English language skills, previous employment and education.

However Mrs May has been a long-term critic of the approach because it grants migrants automatic entry if they have the right number of points, regardless of whether they have a job lined up.

She said in June 2010, shortly after her appointment as home secretary:

"Under the points-based system the impetus is with the individual migrant: if they have the right number of points, they can decide whether they want to try to come into the UK.

Under our system, we are saying, 'We do want to welcome the brightest and the best, but we recognise that it is necessary to have a limit because we want to ensure that we are able to control immigration."

The approach has been heavily criticised by migration experts, who have pointed out that the system is actually used to increase the level of migration.

Lord Green of Deddington, the head of Migration Watch, has described a points-based system as "fool's gold" and called for a work permit system to be introduced instead.