Members of the party voted in Brighton to ramp up the price of permits as part of a raft of changes to the UK’s current border controls.
They called for employers to be charged a percentage of the starting salary of the immigrant worker receiving the permit.
The extra money would be used to retrain British workers in sectors affected by immigration, according to the policy paper Immigration in the 21st Century.
Other measures in the plan include introducing a National Border Force and offering those who have lived illegally in the UK for 10 years the opportunity to earn citizenship.
Liberal Democrat shadow home secretary Nick Clegg said: “This is a humane, workable and principled approach to immigration that is a million miles removed from the shameless populism and blinkered prejudice that has dominated the debate for too long.”