Fianna Fáil is calling for a referendum on reforming the Seanad if it survives the vote on abolishing it.
Micheál Martin said the party will launch its own proposals for reforming the Seanad before the referendum in October.
Fianna Fáil is the only major party calling for a No vote in the referendum.
It says if the public votes No in the first referendum, it will push forward for plans to hold a second one to reform the Seanad properly.
"What the government is proposing is halving the amount of scrutiny that's currently in the system, inadequate as that scrutiny is," Martin said.
He encouraged people to vote no against the government's abolition plans knowing Fianna Fáil will support alternative reform proposals.