In 1976, he, along with Jim Sillars MP and John Robertson MP left the Labour Party to form the Scottish Labour Party (SLP). By 1979 the SLP had collapsed and Neil fell out of active politics until 1985 when he joined the Scottish National Party (SNP).
Neil would go on to become the SNP's Publicity Director, and then in charge of the party's policy, as well as a candidate in the 1989 Glasgow Central by-election, and candidate in the 1992 and 1997 General Elections.
In 1999 he was elected SNP MSP for Central Scotland in the first Scottish Parliament.
The following year he stood unsuccessfully for the leadership of the SNP against John Swinney in a hard fought contest.
Neil is unsurprisingly given his background on the left of the SNP, and is known as a fundamentalist, critical of the gradualist wing.
In 2003 he was re-elected by the people of Central Scotland to the Scottish Parliament.