Is it true that leaving a TV blender can opener etc plugged in still uses as much electricity as using it?

Kinda-sorta, but probably not.

Anything that has a stand-by mode, a built-in clock, A LED shining or anything like that will use a littlepower as long as it's plugged in.

It'll use a lot more power while actually being used, but it's possible that all that time on stand-by together will require as much energy as a few moments of usage.

A blender or a can opener are usually simple devices that don't have any clocks or indicator lights, so they are quite unlikely to use any power while in stand-by mode. A TV however will pull a few watts even if it isn't turned on.