Wales Bill claws back power from assembly, Plaid Cymru claims
Plaid Cymru has said it will vote against UK government plans for further devolution unless they are changed.
The party claimed the draft Wales Bill would see Westminster "clawing back" powers from the assembly.
Plaid said its three MPs would vote against the bill in the Commons while its AMs would reject any related measure in the Senedd.
Welsh Secretary Stephen Crabb has said he thought the bill as it stood kept too many powers at Westminster.
More power over energy, transport and assembly elections is being offered, under a "reserved powers" model where anything not listed as the responsibility of Westminster is assumed to be devolved.
Opposition parties have said the list of reservations is too long, with First Minister Carwyn Jones claiming the bill effectively proposes an "English veto" over Welsh legislation.
Plaid Cymru Leader Leanne Wood claimed the bill undermined the spirit of the 2011 referendum which backed law-making powers for Wales.
In a letter to the prime minister, she said: "Throughout the process of arriving at the draft Wales Bill, Plaid Cymru representative have participated in good faith.
"However, we cannot and will not accept a bill that claws back powers to Westminster and that undermines the 2011 settlement."
Hywel Williams, Plaid Cymru's leader in parliament, said the issue of UK ministerial consent for Welsh laws was "clearly a stumbling block" and represented a "power grab" from Westminster.