In the local elections in May 2002 they got 366 votes (162 in Bethnal Green North and 204 in Millwall).
In the General Election in 2001 they got 3,010 (1,267 in Bethnal Green and 1,743 in Poplar & Canning Town).
In the 1997 General Election they got 6,199 (3,350 and 2,849 respectively).
If you want details for by-elections in individual Council seats since 2002 (or between 1998 and 2002), try
www.gwydir.demon.co.uk/byelectionswhich has details of all local by-elections on a week-by-week basis. It is done in chronological order for the whole country rather than by local authority, but you might be able to find links to specific areas.