Invercargill MP Sarah Dowie has a future in the National Party despite being under police investigation, leader Simon Bridges says.

Ms Dowie is suspected of sending an abusive text message to former National MP Jami-Lee Ross in which she told him: "You deserve to die."

Mr Ross says the message contributed to his breakdown in October, which saw him sectioned under the Mental Health Act.

But Mr Bridges is sticking by the former lawyer and dancer, who's held the Invercargill seat since 2014.

"Do I have confidence in her? Yes I do," he told The AM Show on Monday.

"She's been an effective, hard-working MP. Look, it'll be tough right now, but I think if she can get out demonstrate that again... she can be again an effective MP."

Mr Bridges said he didn't condone what Ms Dowie allegedly said in the text, but it had to be understood in context.

"Everyone that I've been talking to can see what this is - and that's a personal relationship that's gone badly wrong."

He won't even be standing her down while the police investigate the complaint against her, which was laid anonymously.

"I don't think that in and of itself is something in which you'd do that."

Ms Dowie is ranked 41st in the National Party caucus.

She is yet to be charged under the Harmful Digital Communications Act, but faces being expelled from Parliament if she's charged and found guilty.

Newshub.