Nationalist MSP Bruce Crawford, the convener of the devolution committee, made the claim in a letter to the Secretary of State for Scotland, David Mundell.
The SNP MSP said the UK government’s Scotland Bill has “not yet been sufficiently amended to meet all of the recommendations” required to meet the spirit and substance of the Smith Commission.
Mr Mundell previously said that ministers would put “substantive” changes to the bill when it comes before MPs in the autumn.
Opposition parties have said that the UK government’s proposals on welfare did not fulfil the Smith Commission, which was set up after the independence referendum result.
Mr Crawford said the plans still fell short of the Smith Commission ahead of the Bill reaching report stage in the Commons – the final opportunity for the UK government to make amendments before the legislation goes to the Lords.
He said: “At this stage, some welcome progress is being made but, for a majority of areas we have looked at, the Bill has not yet been sufficiently amended to meet all of the recommendations upon which we are all agreed in order to fully implement the Smith Agreement.”