Australia plans to toughen laws allowing overseas workers to plug short-term labor needs and skills shortages as some employers are exploiting the system, Immigration Minister Brendan O'Connor said.

"There is no reason why we wouldn't be looking to properly protect the efficacy and integrity of this scheme by way of legislation," O'Connor said in a Sky Television interview on Sunday. "What we've got to do is really remove the loopholes."

Prime Minister Julia Gillard's ruling Labor party is seeking to gain momentum with voters before the Sept. 14 election after trailing in opinion polls for more than 18 months. The so-called 457 visa program has been backed by mining magnate Gina Rinehart as necessary to fill labor shortfalls that may threaten the nation's investment pipeline that reached $280 billion as of Oct. 31, according to a government research department.