The Tories have repeatedly attacked what they describe as Mr Brown's infrequent appearances in the House of Commons.
But friends of Mr Brown vigorously defended his record last night, pointing to his work for his constituency and global roles advocating education across the world.
This week, the Labour MP helped launch a campaign to find 300,000 school places for Syrian refugee children.
Last week, he used a keynote speech to set out his vision for Scotland's future. He has also campaigned locally on a number of issues including the closure of Remploy factories and the clean up of Dalgety Bay in recent weeks.
The "zero hours" jibe came from Scotland Office minister David Mundell.