Teen idol Hilary Duff has apologised for dressing up as a pilgrim while her boyfriend imitated a Native American at a Halloween party.

The actress, known for her Disney channel series Lizzie McGuire, dressed in a pilgrim top and hat at the Casamigos Tequila Halloween Party in Los Angeles.

Her boyfriend, personal trainer Jason Walsh, painted his face and put on a headdress to imitate a Native American.

Duff received a swift social media backlash after pictures from the party were posted online. 

No @HilaryDuff Traditional dress is not a costume and you being dressed as a pilgrim proves to me how insensitive and ignorant you are, one Twitter user wrote.

Some called the costumes racially insensitive, pointing out the timing couldn’t be worse after the Dakota Pipeline protests.

The actress and her boyfriend were quick to issue apologies on their social media accounts, writing they were sorry and meant no disrespect.

I am SO sorry to people I offended with my costume.It was not properly thought through and I am truly, from the bottom of my heart, she wrote.

The Casamigos Halloween party on Friday night was their first appearance as a couple.

(c) Sky News 2016: Hilary Duff ‘so sorry’ for pilgrim Halloween costume