Both looked fudged so will need changing anyway.more likely poor connection between socket and pins on plug, change both problem sorted
Wot 'e sedThe issue is the fact the extension is poor quality, throw it away, either fit a socket closer to the drier or move the drier closer to a socket, those multi extensions may be fine for computers,TV's or audio equipment, but no good for something like a tumble drier.
Cut the plug off and replace.
Or at worst make an extension using something like this http://www.screwfix.com/p/masterplug-heavy-duty-rewirable-13a-1-gang-single-pole-socket-white/89675 with a piece of 1.5 flex and as short as you can get away with.