The Abbott government will unveil its new childcare assistance package with much fanfare on Sunday but Labor and the crossbenchers warn it could face a tough time in the Senate if it's tied to cuts to other benefits.

Prime Minister Tony Abbott said on Saturday the package – the major sweetener of the government's make-or-break second budget – would be a big improvement on the existing childcare system and he was confident it would be well received.

Opposition parties are wary of the assistance package, especially if it means cuts to Family Tax Benefits. Credit:Getty

"The existing situation is complex, it's confusing and it's narrowly focused," he told reporters in Darwin. "So we do want a childcare system that is simpler, which is fairer, which is more affordable and more accessible."

The government is positioning the package as a workforce participation measure – a way to get mums back into the workforce.