Miley Cyrus' mother has slammed a report the newly-engaged teen star is pregnant.

Editors at a U.S. magazine alleged this week that the former Hannah Montana star and her actor boyfriend Liam Hemsworth got engaged last month because she has "a baby on board".

But Cyrus' mom Tish has taken to her Twitter.com page to blast the speculation, insisting the story is false.

She writes, "So sad that the nasty tabloids have to make up stories to sell their trashy mags. Cant (sic) they just leave these 2 alone and let them be happy?... makes me so sad. This should be the happiest time of there (sic) lives and it makes me sick they USE her to sell mags... Thanks to all the Miley supporters who LOVE her..." (ZN/WNWCGC&WNTWT/MT)