A Commons motion to impeach Tony Blair for "gross misconduct" over the Iraq war is being published next week.
Plaid Cymru's Adam Price says Blair must be brought to book
Parliamentary officials have approved the motion's wording and will allow it to be tabled on Wednesday - the day after the Queen's Speech.
MPs will have the chance to sign the order paper. The Speaker will then decide whether to allow a debate on it.
Plaid Cymru's Adam Price said 30 MPs have agreed to sign the motion which charges Mr Blair with improper conduct.
The allegation against the prime minister would be that in making the case against Iraq he was guilty of a serious breach of constitutional principles.
Mr Price said that the impeachment process had now been established as part of British Parliamentary practice.
It closed a "gap in the constitution" which had meant that while the prime minister had to hold his ministers to account, there was nothing to hold the prime minister to account if he were to mislead Parliament.
If passed, the motion would set up a committee of MPs to examine Mr Blair's conduct over the war.
"It (Wednesday) will be an historic occasion as it will be the first time since Trafalgar, we think, that an impeachment motion has appeared on an order paper," Mr Price added.
The Camarthen East MP said his motion had cross-party support, but few Labour MPs are thought likely to sign it for fear of losing the party whip.
Conservative MPs are being instructed not to sign the motion and the Liberal Democrats are divided on the issue.
Downing Street says Tony Blair has already been cleared by four separate inquiries into the pre-war intelligence on Iraq.
Donald Anderson, the Labour Swansea East MP and chairman of the Commons foreign affairs committee, has dismissed the plan as a "no-hoper" and a "political stunt".