It was an afternoon to forget for City, that began with Dartford's Richard Sho-Silva putting the home side ahead after nine minutes.
Lyle Della-Verde, Alfie Pavey and Lee Noble also scored in the first-half for the Darts as Oxford's Freddie Grant was sent off before half-time.
A second half hat-trick from Warren Mfula only rubbed salt into City's wounds, leaving boss Jones livid, he said: "I'd like to apologise to the people that travelled from Oxford. There's no excuse to get beat 7-1, it's poor to say the least.
"We've come here and been totally bullied in the first-half of the game and we've been done by five set plays which is totally unacceptable. We showed no desire to defend them and some of our play that led to it was sloppy.
"We've had our pants pulled down, for want of a better expression. You just quite simply can't defend like we did today. We got every single little detail wrong. I hope the players are hurting just as much as I am because that is my week completely and utterly ruined.
He continued: "We told the players exactly what we think. A lot of people put a lot of effort into running this club to provide a team at National League South level and we've been badly let down today.
"That's not just trying to parcel the blame onto the players, I'm the manager, I selected the players, I selected the shape so I've got to take responsibility for that. They'll be no one looking harder at themselves than me, I just hope some of the players do the same thing.