She said the Conservatives had been wrong to focus on net migration and should have strengthened border controls to tackle illegal immigration, "where enforcement has got worse".
"[Home Secretary] Theresa May's obsession with the target has led her to target valuable university students, who bring billions into Britain whilst doing nothing to make the labour market fairer for local workers, preventing undercutting by exploitative employers or putting in place proper border controls so we can count people in and out to enforce the rules," she said.
UKIP, which campaigns for Britain to leave the EU and wants an Australian-style work permit system, said the government "should be ashamed of its abject failure to keep control of the constantly rising numbers of those arriving here".