The chief executive of a group that produced a wildly popular video about African warlord Joseph Kony answered its critics on Monday with a second film on YouTube, defending its tactics and spending practices.

“I understand why a lot of people are wondering, ‘Is this just some slick, kind of fly-by-night, slacktivist thing?’ when actually it’s not at all,” said Ben Keesey of Invisible Children. “It’s connected to a really deep, thoughtful, very intentional and strategic campaign.”

In an online video that runs more than eight minutes, Keesey acknowledges the sting of criticism since Invisible Children released the video “Kony 2012” last week, becoming an internet sensation with nearly 75 million views on YouTube alone. The overnight success has earned the San Diego-based non-profit organisation widespread praise and brought heightened scrutiny.

The group has been criticised for not spending enough directly on the people it intends to help and for oversimplifying the 26-year-old conflict involving the Lord’s Resistance Army and its leader, Kony, a bush fighter wanted by the International Criminal Court for crimes against humanity.

Keesey, 28, said “program expenses” – money that directly benefits their cause – accounted for 80.5 per cent to 85.7 per cent of total annual spending from fiscal 2007 to 2011. Overhead expenses grew last year, largely due to a $330,000 private foundation grant that was designated specifically for operations.

“This is actually a really good thing to help Invisible Children continue to be more efficient and to increase the quality of our work for years in the future,” he said.

Keesey said travel and transportation expenses – which totalled more than $1 million last year – include costs for 3,000 free movie screenings a year to spread the word about Kony and the LRA.

“Some people have characterised that and said, ‘Is that just the management team flying around and staying in nice hotels. No, not at all. That’s totally not true,” he said.

Production costs -more than $850,000 last year – have been another target for critics. Keesey said those costs are for items like T-shirts, DVDs and bracelets “that fund all of our work.”

Invisible Children reported revenues of $13.8 million last year – aided by a $2 million contribution from The Oprah Winfrey Foundation – up from $8.3 million a year earlier, according to its Internal Revenue Service filing. Expenses grew to $8.9 million from $8.1 million, yielding a surplus of $4.9 million.