The singer sparked speculation she was expecting after being snapped looking a little curvier while out in London over the weekend.
'I'm not pregnant. FYI,' she writes on her Twitter.
Last week, Lily, 25, revealed she's taking a break from her music career to start a family with her boyfriend Sam Cooper, 44.
'I'd like to have a child within a year. I'd want to be really hands-on for the first two or three years of having a little one,' she told Absolute Radio.
'I don't want to leave them. It'll be a minimum of four or five years before I make a record again.'
Lily suffered a miscarriage in January 2008 while in a relationship with Chemical Brothers star Ed Simons.
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