Scotland's Brexit Minister has urged MSPs to back calls for changes to the Repeal Bill to guarantee protection for devolved powers.
The Bill is designed to transpose EU law into British law so the same rules apply on the day of Brexit as the day before, while giving parliaments and assemblies in Westminster, Edinburgh, Belfast and Cardiff the power to drop or change them in the future.
The First Ministers of Scotland and Wales, Nicola Sturgeon and Carwyn Jones described it as a "naked power grab" because it does not immediately return EU powers to devolved administrations and said they would withhold legislative consent from the Bill as it stands.
However, Scottish Secretary David Mundell said the legislation would result in a powers "bonanza" for Holyrood.
Now, Scotland's Brexit Minister Michael Russell has written to all MSPs seeking support for the Scottish Government's position.
He said: "Scotland will stand the best chance of keeping control of its devolved powers if the Scottish Government can act with the full backing of our national Parliament.
"The First Minister has already called on Members of the Scottish Parliament to join us now, with no equivocation, to back demands for the democratically elected Scottish Government to be at the table in the UK's Brexit negotiating strategy. But we also need to make a stand against the UK Government retaining powers that rightfully should come to Scotland once repatriated from the EU.
"Scotland has been able to make its own decisions on Health, Justice, Education and many more since 1999 and we simply ask for a promise from the UK Government, to be written in the EU (Withdrawal) Bill, that Scotland – along with Wales and Northern Ireland – receive the powers that are justly theirs."
In his letter, Mr Russell highlights concerns that the bill enables UK-wide frameworks on devolved matters to be "imposed" by the UK Government rather than "agreed" with the devolved administrations.
He adds: "We are also concerned that the scheme in the bill for correcting devolved law is unlikely to be workable in its current form. It creates a complex division of decision-making responsibility that does not reflect the reality of devolution.
"In particular, it empowers UK Ministers to make changes in devolved policy areas without any involvement of either the Scottish Government or the Scottish Parliament. This includes policy areas, such as the Scottish justice system, where the Scottish Parliament has primary responsibility."
Scottish Liberal Democrat business manager Mike Rumbles said the Bill is a "huge executive power" grab and said his party would work with others to protect devolution.
He said: "Scottish Liberal Democrats will work with other parties to find common ground in support of vital protections from workers' rights to the environment, as well as ensuring that the principles of devolution are respected.
"It is essential that the Scottish Government and the Scottish Parliament have a central role in devolved policy areas and that any powers repatriated from the EU in these areas come to Scotland."
A UK Government spokesman said: "It is the expectation of the Government that the outcome of this process will be a significant increase in the decision-making power of each devolved administration.
"We welcome the Scottish and Welsh governments recognising common frameworks may be needed in some areas. Our aim is to establish common frameworks only where they are needed."