In 2004, J.-C. Aval, F. Bergeron and N. Bergeron studied the algebra of diagonally quasi-symmetric functions DQSym in the ring Q[x,y] with two sets of variables. They made conjectures on the structure of the quotient Q[x,y]/〈DQSym〉, which is a quasi-symmetric analogue of the diagonal harmonic polynomials. In this paper, we construct a Hilbert basis for this quotient when there are infinitely ma...