New mums will be able to claim maternity leave from their employers as well as the government scheme if Labor is elected on July 2.

A year ago on Mother's Day former Liberal treasurer Joe Hockey said claiming both schemes was `double dipping' and the government put forward legislation to limit maternity leave to just one source of income - but that has yet to become law.

But last week's budget confirmed the government's commitment to a crackdown on paid parental leave `double-dipping'.

Opposition Leader Bill Shorten told the Seven Network, just hours before Prime Minister Malcolm Turnbull is expected to visit the governor-general seeking a July 2 double-dissolution election, that Labor will make sure that working mums aren't penalised.

Labor says under its policy families with new babies will be as much as $11,800 better off than they would be under the Liberals.

A preliminary estimate by the independent Parliamentary Budget Office says it will cost $1.4 billion over the four-year budget estimates.

"Labor will put people first. We will protect paid parental leave for young families," Labor said in statement.