A measure giving the Welsh assembly more powers over housing is unlikely to be passed in this Parliament due to a lack of time with the general election.
It is thought unlikely that the housing and local government Legislative Competence Order (LCO) will make it.
Jocelyn Davies, the assembly government's deputy housing minister, appealed to all involved to ensure it gets through.
But the Conservatives say they have "fundamental objections" to two parts.
Ms Davies, appealing for backing from all sides, said: "It has overwhelming support from the housing sector in Wales and received positive and constructive scrutiny from the National Assembly and the Welsh affairs committee."
But David Jones, the Conservative shadow minister for Wales, said his party would support the measure if the two clauses were removed.
The Tories said one of these clauses would suspend the right to buy both social and council housing.
It could also give the assembly the ability to abolish the right to buy, but Conservatives said as the assembly government confirmed that it did not intend to do so, it should be left out of the measure.
The Conservatives said the other clause could allow Gypsy and traveller sites to be built contrary to local decisions.
Welsh Secretary Peter Hain has also urged all parties to support the measure before Parliament is dissolved, or it would be "a huge blow for homeless and vulnerable people".
Welsh Liberal Democrat housing spokesperson Peter Black claimed the Conservatives were " scaremongering and misleading the public" on the powers that would be available to ministers if the measure was approved.
He said the Tories' claim on Gypsy and traveller sites was not supported by the facts, and said their location and the approval process would remain with the local planning authority.
• Several measures from the Budget will also be abandoned due to lack of time.
Labour has had to sacrifice a 10% tax increase on cider, a new tax on phone lines to pay for super-fast broadband, and the scrapping of tax relief on holiday homes.