ACT Party leader David Seymour missed his opportunity to vote against the speed of the Government's gun law reform, because he was outside talking to journalists.

Seymour was so caught up talking about his objections to the speed of the proposed gun law reform that he missed being in the House to vote against it.

The blunder was met with "a momentary laughing fit from all sides" of the chamber, Green MP Golriz Ghahraman wrote on Twitter.

"David Seymour just missed opposing urgency on gun law reform because he's late to the House," she tweeted. "That's one way to avoid being on the wrong side of history."

When Seymour did make it into the House, Ghahraman said he frantically read through the Speakers' Rulings.

"So much schadenfreude," she wrote, accompanied by a mocking 'cry' emoji.