The same source also told The Guardian that the ministers aimed to secure a deal as quickly as possible to provide certainty to British business.
The uncertainties surrounding Brexit has already contributed to a sharp drop in new business reviews for the ad industry.
The report by AAR new business pulse report released yesterday showed that advertising appointments were down 3.2% driven by a drop in digital that saw the number of appointments at less than half that of 1H2016.
AAR chief executive Kerry Glazer said the figures reflect a fluctuating market due to a second quarter that was disrupted by a late Easter and the run-up to the election, which reignited concerns about Brexit negotiations.