Communications Minister Stephen Conroy had planned for the internet filter to be debated this week, but his office confirmed the drafting of the legislation was still not complete and discussions with ISPs and other stakeholders on outstanding issues were still taking place.
With only three Senate sitting days in May during the Budget session, and a growing backlog of Government business, it is unlikely the filter will be presented before June.
"The Government will take the time to ensure that it gets the legislative framework right," a spokeswoman for Senator Conroy said.
"Discussions with ISPs and owners of high traffic sites on the implementation of ISP filtering are ongoing. The Government is also considering the responses to the consultation paper on improved transparency and accountability measures which will feed into the legislative framework."
"The Bill will be introduced when these processes are completed," the spokeswoman said.
It is not clear whether the internet filtering plan has a chance of getting through the Senate. The Greens are opposed to the scheme, and the opposition says while it supports in principle measures to protect children online, it has deep reservations about mandatory ISP level filtering.
Shadow communications spokesman Tony Smith said the coalition will wait until the draft legislation is tabled before it formalises a policy on the issue.
The filtering scheme is not the only Communications portfolio legislation being pushed back. The extensions to the Do Not Call register to include businesses was to have been put to the Senate this week, but also looks certain to be pushed back until the June sittings.