A small but vocal crowd had a clear message for National's Mana by-election candidate, Hekia Parata, when she visited Raumati South today: "Nats go home".

The group of about 30, mostly women and children, were protesting against a planned motorway for the area.

Alliance for Sustainable Kapiti chairwoman Marie O'Sullivan told NZPA the aim of the protest was to register their opposition to the motorway and to let the Government know locals were not happy about it.

"It's going to be right over peoples' back fences," she said.

"We don't see any economic benefit from this road for us locally or in the national interest.

"It's benefit-cost ratio is very low and we don't even understand how it came to be approved."

Mrs Parata is contesting the November 20 by-election and her campaign launch rally today involved a whose who of National Party ministers and MPs, including Prime Minister John Key.

The by-election in the safe Labour seat has been caused by the resignation from Parliament of Winnie Laban, who is taking up a position at Victoria University.