A voice like an indignant dormouse
I don’t know if you read your own link properly but that insult was aimed at Jenny Jones not Natalie Bennett :
“Hosting the press conference was Jenny Jones, the seaweed-haired Green Party peer with a voice like an indignant dormouse”.
I like Jenny Jones, although I can understand why the Daily Telegraph writers might not like her. Here she is laying into Daily Telegraph columnist Boris Johnson for his appalling slur against cyclists in which he falsely claimed that cyclists were responsible for the majority of accidents :
I would rather have seaweed-haired Jenny Jones with her voice like an indignant dormouse speaking on behalf of me than the tousled haired blonde with the baritone voice.