Plaid Cymru has voted to send people to the House of Lords to represent the party - reversing its historic opposition to the move.
Elfyn Llwyd argues that Plaid needs peers in the Lords
Plaid had always rejected the policy of creating its own peers because it wanted the Lords to be fully elected.
But Plaid parliamentary leader Elfyn Llwyd argued new powers for the Welsh assembly which are ratified by Parliament mean the party needed peers.
Members voted on the policy change at a meeting in Aberystwyth on Saturday.
The process of nominating and selecting suitable candidates to go to the Lords will now begin.
A meeting to decide the matter will be held in January.
At Plaid's conference in September representatives agreed to review the policy after Mr Llwyd argued that peers were required to ensure planned legislation for Wales was not blocked at Westminster.
The members were also required to reflect the views of the people of Wales in the Upper Chamber, he said.
The Welsh assembly's new powers under the Government of Wales act allows it to make its own laws in devolved areas, with the permission of Parliament.
Mr Llywd warned that many in the House of Lords might want to block such permission, known as Orders in Council.
The Welsh assembly's presiding officer Dafydd Elis-Thomas, the only Plaid party member to sit as a peer, also believed his party's policy should change.
He has sat as a cross bencher, not as a party appointee, since 1992.
Speaking after the vote, he said: "I think it's long overdue because we have not been represented as a party and as a point of view in the politics of Wales in the second chamber of the UK, especially now when legislation, the orders that empower the assembly, are being made through Westminster."
But there was some opposition within the party ranks.
Bethan Jenkins AM argued the Lords needed to be completely reformed before Plaid representatives were sent there.
"We have seen with the cash for honours scandal and all the problems that this has induced that the Lords is not a very democratic institution," she said.
"We should be utilising our resources in other ways.
"We should be looking forward to the referendum in 2011 or before - that is where we need to put our best people."
Plaid last discussed this issue in 1999 when a vote went against the motion.
Meanwhile members of Plaid's national council also decided not to back its vice president's paper which queried the party's support for a new military training academy in the Vale of Glamorgan.
MEP Jill Evans, who also chairs CND Cymru, said the proposed 5,000-job centre was inconsistent with the spirit of the party's defence policy.
The council said more work was needed on the paper.
A party spokesman denied that they were avoiding the issue.