More than 64,000 people are in Australia illegally after overstaying work and tourist visas, with the federal government estimating as many as 12,000 have been here for more than 20 years.

New figures from the Department of Immigration and Border Protection show temporary visitor visas are the mostly likely to be abused in Australia, while Malaysian nationals made up the largest group of unlawful non-citizens in the country last financial year.

More than 64,000 people are believed to have over stayed visas in Australia Credit:iStock

There were nearly 10,000 Malaysians recorded as having overstayed visas in 2016-17, along with about 6500 Chinese nationals and 5170 from the United States.

Countries outside the top 15 most likely to overstay represented nearly 18,000 in the category. About 3700 UK nationals overstayed, ahead of 2780 Indonesians and 2730 Indians.