'Parliament is to be given a take-it-or leave-it vote on the final Brexit deal before the UK leaves the EU.
Brexit Secretary David Davis said the terms of the UK's exit, such as money, citizen rights and any transition must become law via a new Act of Parliament.
Labour welcomed a "climbdown" but some MPs warned of a "sham" if ministers could not be asked to renegotiate.
Sources have told the BBC some Tory rebels were unimpressed, with one saying the promise was "meaningless".
BBC political editor Laura Kuenssberg said the announcement was significant because it represented a big concession to potential Tory rebels and Labour MPs at a highly important moment in the Brexit process.
It comes as MPs prepare to debate key Brexit legislation later this week with the government facing possible defeat on aspects of the EU Withdrawal Bill, which will convert EU law into UK law.'
Read More: Parliament to get binding vote on final Brexit deal