Washington: A Massachusetts state senator who opposes President Donald Trump's immigration policies was mistakenly booked on Fox News, and she used the airtime to criticise Trump's "illegal and inhumane" treatment of migrant families crossing the US-Mexico border.

Barbara L'Italien, a Democrat, appeared Monday on Fox & Friends First, instead of the intended guest, Democratic congressional candidate Ann Kirkpatrick, who has openly supported US Immigration and Customs Enforcement (ICE). A spokesman for Ms L'Italien said in a statement that "due to a Fox News error," Ms L'Italien was contacted and asked to share her views on ICE and decided to use the opportunity to "make a statement straight to Trump".

US President Donald Trump boards Air Force One last week. Credit:AP

"I'm actually here to speak directly to Donald Trump," she said during the broadcast. "I feel that what's happening at the border is wrong."

The senator said she has four children and believes that "separating kids from their parents is illegal and inhumane".