Plaid Cymru bid for official opposition role at Westminster
Plaid Cymru has asked to be designated the official opposition for a House of Commons debate on devolution, as Labour is "too busy tearing itself apart".
MPs discuss the Wales Bill - to hand energy, transport and other powers to Cardiff Bay - on Tuesday.
Resignations from Jeremy Corbyn's front-bench mean Labour has no shadow Welsh secretary or junior spokespeople.
An SNP bid to become the official opposition for all Commons business was rejected by the speaker on Wednesday.
Nia Griffith resigned as shadow Welsh secretary on Monday, along with deputy Susan Elan Jones and parliamentary aide Gerald Jones.
Plaid Cymru's Westminster group leader Hywel Williams said the Wales Bill could not be debated with an empty opposition front bench.
"On Tuesday, the House of Commons will discuss crucial amendments to the Wales Bill, including on the very foundations upon which all future Welsh legislation will be formed," he said.
"It is unthinkable that this should take place without a strong opposition in place.
"The Labour Party, too busy tearing itself apart, has no shadow cabinet, and no shadow Wales team to hold the Tories to account."
He added: "It is clear that the Labour Party is not fit to perform that role so that duty must fall to Plaid Cymru."