Under-fire web firm Mozilla has named an insider as interim CEO after its ex-chief executive stepped down amid vigorous criticism over his anti-gay marriage stance.

The company behind the successful Firefox browser has now named Chris Beard, its former CMO, as interim boss, as it seeks to quell discontent among users.

Mitchell Baker, the executive chairwoman of the Mozilla Foundation, the non-profit organisation that owns Mozilla, said in a blog post: "Mozilla finds itself in the midst of an unexpected leadership transition.

"In this time of transition there is no better person to lead us. Chris has one of the clearest visions of how to take the Mozilla mission and turn it into programs and activities and product ideas that I have ever seen.

"Chris is the right person to lead us through this time and he is a strong candidate for CEO."

Baker also appointed Beard to the board of directors and admitted that Mozilla must "act quickly and decisively" as it tries to build on its products including Firefox for Android and the Firefox mobile OS.

Beard was part of those launches, as well as being involved with Mozilla since before the release of Firefox 1.0.

Brendan Eich was in charge for just 11 days before he announced his resignation in order to "take a rest", after prompting anger among Mozilla product users for his $1,000 donation in 2008 to a Californian anti-gay marriage bill Proposition 8.

After last month’s appointment of Eich, dating site OkCupid urged its users to stop using Mozilla’s Firefox browser in protest against the anti-gay views of Mozilla’s new CEO and directed consumers to use other Internet browsers, such as Chrome.

In addition, upon Eich’s promotion, app development firm Rarebit pulled its apps from Firefox browser.

Eich co-founded Mozilla with Baker back in 1998, but his position became untenable soon after he took the reins.

Baker said of the incident: "We didn’t act like you’d expect Mozilla to act. We didn’t move fast enough to engage with people once the controversy started. We’re sorry. We must do better."