The Sierra Club (search) is one of the nation's most influential environmental groups, but these days, along with fighting for the environment, its members are fighting among themselves. The issue is immigration, on which the Sierra Club is neutral, at least for now.

"We are on a trajectory to have a billion people here in the next hundred years or so," said Ben Zuckerman, an anti-immigration Sierra Club board member.

Zuckerman is in the minority, but five board seats are now up for grabs, and half of the candidates are anti-immigration (search). If they can grab three of the five seats, they will control policy.

Some Sierra Club activists feel an anti-immigration message will cripple the organization's impact.

"Many minority communities, especially those groups the Sierra Club has worked with on environmental justice issues, are very alarmed at this movement within the Sierra Club," said Sanjay Ranchod a Sierra Club board candidate.

This campaign is far from a friendly family feud, with some current members claiming the anti-immigration candidates are joining forces with animal rights activists (search) and white supremacy groups just to get elected.

The anti-immigration candidates are firing back with a lawsuit, claiming current Sierra Club officials are using the organization's money to support their own candidates.

Click here to watch a report by Fox News Channel's Trace Gallagher.