A Vice News documentary profiling Corbyn that aired earlier in the day showed his strategy director Seamus Milne accusing Labour staffers of leaking Prime Minister's Questions (PMQs) to Prime Minister David Cameron ahead of the PMQs.
"I wanted you to know, directly, that your work does not go unappreciated or unnoticed… Every single one of you is an integral and vital part of that march," Labour General Secretary Iain McNicol wrote in a letter to party members seen by The Telegraph.
"Every day, including weekends and bank holidays, you work to put our values in to action and for that I am extremely grateful and in awe of your sheer ability to get things done," he reiterated.
In the documentary, Milne argued that the alleged "very annoying" leaks give the Conservative Party "a little bit of extra time" and "the advantage on TV."
PMQs are a weekly round of half-hour sessions allowing British lawmakers, Corbyn first among them, to submit questions to Cameron.