axis label justified

Hi, I am trying to make my axis labels left justified,
and have used adj=0 in the axis() without success. Can
anyone have a suggestion?

axis(2,at=1:50,labels=paste('a',1:50,sep=''),las=2,cex.axis=0.5,adj=0,tck=0,mgp=c(3,0.5,0))

Thanks