A government bid to find a compromise to win over rebels before the Commons Brexit vote has run into criticism.
A Tory backbench amendment – understood to have No 10’s backing – offers MPs more of a say over the contentious issue of the Northern Ireland backstop.
DUP leader Arlene Foster dismissed it as “legislative tinkering” while Tory Brexiteers said it was “desperate”.
Many MPs have expressed concerns about the backstop, aimed at preventing a “hard border” on the island of Ireland.
It would mean Northern Ireland staying aligned to some EU rules, which many MPs say is unacceptable.
The UK would also not be able to leave the backstop without EU agreement.
Cabinet ministers are travelling around the UK on Friday as Theresa May continues to seek support for her Brexit deal.
The withdrawal deal negotiated between the UK and EU has been endorsed by EU leaders but must also be backed by Parliament if it is to come into force.
MPs will decide whether to accept it next Tuesday, but dozens of Tories are expected to reject it, as will the DUP, whose support keeps Mrs May’s government in power.