The Welsh Assembly's presiding officer is refusing to attend an event to mark the renaming of the Second Severn Crossing after the Prince of Wales.
Elin Jones said it was "interesting" for the Welsh Secretary Alun Cairns to hold the event after the UK government turned down a request to back a tidal lagoon in Swansea Bay.
Fellow Plaid Cymru AMs have criticised the lack of public consultation over the bridge renaming.
The Wales Office was asked to comment.
"Thanks for [the] invite", Ms Jones said on Twitter. "I won't be there."
Revealing the renaming plan in April, Mr Cairns said the "wider, silent majority" of people in Wales would support the honour, to mark Prince Charles's 70th birthday and the 60th anniversary of him being given the title Prince of Wales.
A petition rejecting the plan to change the name of the crossing was signed by 38,000 people.
A spokeswoman at the Wales Office said Ms Jones was invited "in her capacity as presiding officer to an event to mark the renaming of the bridge".
But the Plaid Cymru AM said on Twitter that the email invite came to "Elin Jones AM not Llywydd" (presiding officer).