Abstract: The invention relates to a resin composition based on a urea-modified phenol-formaldehyde resole which has a formaldehyde/phenol molar ratio of 2 to 5, exhibiting a free formaldehyde content lower than or equal to 3 percent (by weight relative to the total weight of the composition), a free phenol content lower than or equal to 0.5 percent and a dilutability measured at 20° C., of at least 1000 percent and to a process for the preparation of this composition. This composition is characterized in that it contains an overcondensed resole obtained by the condensation of phenol, of formaldehyde, and optionally of urea in basic medium, until the product has a water dilutability at pH 9 that is lower than or equal to 2000 percent, or the product of neutralization of such as resole. The modification of an overcondensed phenolic resole by neutralization with boric acid according to the invention permits the dilutability of the resole to be increased.