Actress and pop singer Lindsay Lohan, 25, has come to the rescue of her 17-year-old sister by denying the rumors that she had plastic surgery.

Lindsay Lohan, who began her career as a child fashion model, posted her views on Twitter on Friday that her younger sister Ali Lohan shouldn't have to defend her changing new look.

I love how haters pick on my sister yet every runway model is just as thin! she wrote. My sister is gorgeous and I'm so proud of her and her career!!!!

Lindsay told GossipCop that her sister would not do any surgery to her body. No way! Never!

Ali Lohan has noticeably changed her look after she signed a contract with famous agency models.

She was spotted with a much altered face when she stepped out with Lindsay in Beverly Hills Wednesday, sparking debate over whether she has had plastic surgery.

Her lips looked plumper, her nose more refined, completely redesigned eyebrows, and more prominent cheekbones. Usually thin, Ali was looked much thinner.

Last month, she signed a multi-year modeling contract with NEXT Model Management. She previously modeled for her sister's 6126 fashion line in its Spring/Summer 2011 campaign.

She represents the future face of fashion and will be a photographer's dream with her chameleon-like beauty, NEXT LA Director Alexis Borges told Just Jared.

The changes on Ali Lohan's face forced people to think if she got a plastic surgery done or whether it was a part of a regular aging process.

Her new look has shocked everyone, even his father.

It's scary to see my daughter looking like this, her father, Michael Lohan, told Radar Online. Ali was always on the thin side, but seeing how much weight she's lost there appears to be a drastic change that concerns me. This industry has a way of having a harmful effect on one's health and well-being. To see what Lindsay has gone through is one thing, I certainly hope Ali isn't going through the same thing.

Aliana has never had any type of plastic surgery in her life, nor has she ever considered it, said Ali's representative.

Ali is growing up; that's all, the representative added.