No first minister "worth their salt" would agree to support the EU Withdrawal Bill in its current form, Nicola Sturgeon has said.
The legislation - designed to transpose EU law into British law so the same rules apply on the day of Brexit as the day before - will see EU responsibilities in devolved areas initially transferred to Westminster.
Both the Scottish and Welsh governments have said they cannot recommend that legislative consent is given to the European Union (Withdrawal) Bill as it stands.
The UK Government said the legislation will allow common frameworks to be created ahead of further devolution but devolved governments say it amounts to a power grab and must be amended.
Speaking to ITV's Peston On Sunday, Ms Sturgeon said she could not commit to backing the EU Withdrawal Bill.
"No, I won't at this stage because we haven't reached the agreement that we would need to reach, and I should say the Welsh Government are in exactly the same position as the Scottish Government," the First Minister said.
"There has been movement on the part of the UK Government - we've welcomed that - but it doesn't yet address the issue of principle at stake.
"We accept, as do Wales, that there will be areas where common frameworks across the UK make sense and that would probably be the case if and when Scotland becomes independent.
"But the question is 'who decides?' and at the moment the UK Government's proposition is that even in areas of devolved competence - agriculture, the environment, fishing, justice - they should be able to impose frameworks on Scotland and Wales, and our position is that where there are devolved areas it should only be by the consent of the Scottish and Welsh parliaments, so I hope we can reach agreement.
"We're working hard towards that, but I'm going to continue to be frank about it - there is an issue of principle at stake that we won't compromise on because if we did we would allow Westminster to exercise a power grab on the responsibilities of the Scottish Parliament and I don't think any first minister worth their salt should agree to that."
Downing Street said on Friday that Theresa May and Ms Sturgeon agreed to work to break the deadlock around the Bill in a phone call after the Prime Minister's most recent Brexit speech.