Plaid Cymru's leader Ieuan Wyn Jones has urged party members at their spring conference to become "part of the politics of the future".
Ieuan Wyn Jones tells the conference Labour let down Wales
Mr Jones also called on Plaid to "embrace change" in next year's Welsh assembly elections.
His speech in Carmarthen came the day after he was again elected overall party leader and Plaid unveiled the biggest image overhaul in its history.
He said the new image and logo pointed to a "renewed sense of optimism".
Plaid is dropping its traditional green colour and "triban" logo, replacing them with a yellow poppy. It will also no longer use the word Cymru in its title branding.
Mr Jones, the Anglesey AM, had been overall leader until three years ago, when he stepped down after election results.
The top job was split, and Mr Jones became leader of the Plaid assembly group, while Gwynedd councillor Dafydd Iwan was elected president.
Now, however, Mr Jones has become leader of the party again, although Mr Iwan remains president.
Mr Jones called on Plaid to help "restore trust" in the Welsh political system, arguing that people felt "badly let down" by Labour in London and Cardiff.
The new leader speaks against the backdrop of the new logo
Mr Jones told the conference: "People lost trust in Tony Blair because of the Iraq war, and now in Rhodri Morgan because he has betrayed the trust of people with disabilities by reneging on the manifesto commitment to provide free home care.
"This follows a catalogue of failures on waiting lists, economic targets, free school breakfasts and the proposed abolition of prescription charges."
Mr Jones told conference members Labour had "run out of ideas and run out of steam" and that the "biggest challenge" in Plaid's history will be to become the party of government in 2007.
But rival parties claimed the image change could not hide the fact the party was losing popularity.