The Abbott government has spent $100,000 on travel costs to send environment department officials to lobby other countries not to list the Great Barrier Reef as in danger.

The figure was revealed in a Senate estimates hearing on Monday after questions from the Greens.

A Senate estimates hearing has been told the Abbott government has spent $100,000 to lobby against UNESCO listing the Great Barrier Reef as in danger. Credit:Ed Roberts

The government has mounted a massive international effort to avoid UNESCO's world heritage committee listing the reef as officially in danger next month.

That has included establishing a dedicated taskforce within the Department of Foreign Affairs and Trade and travelling to each of the 21 countries on the committee.