Plaid Cymru won 17 of 60 assembly seats under Dafydd Wigley in 1999

At Plaid's conference in Carmarthen on Saturday he announced he was seeking nomination for the 2007 election. He is likely to stand on a regional list.

He led Plaid to its greatest success at the first assembly election in 1999, but ill health meant he stood down from the party's top job in 2000.

Mr Wigley, 62, then gave up his Caernarfon seat at the 2003 election.

Mr Wigley, who was made the party's honorary president last year, told S4C that he wanted to re-enter frontline politics.

Political analysts believe he will try to return to Cardiff via the list system as a candidate in either the South Wales Central or North Wales regions.

DAFYDD WIGLEY FACT FILE Born: Derby, 1 April 1943 Educated: Manchester University; industrial economist Married: Elinor Bennett Elected: Caernarfon MP 1974-2001 and AM 1999-2003 Sponsored: Disabled Persons Act of 1981 Plaid Cymru: president 1981 - 4 and 1991 - 2000

The party currently has a vacancy in South Wales Central, which covers Cardiff, Vale of Glamorgan, Cynon Valley, Pontypridd and Rhondda.

One of its current two AMs for the area, Owen John Thomas, will be standing down at the next election.

Supporters of Mr Wigley have said he could be about to put himself forward for that vacancy.

He became MP for Caernarfon in 1974, standing down in 2001. He served as party president twice, from 1981 - 1984, and again from 1991 - 2000.