Williams' technical director Paddy Lowe says the team’s car is much quicker than their points tally for 2017 shows.
Lowe claims the FW40 has the potential to be extremely quick but has not shown it yet, admitting to be disappointed with first half of the 2017 season.
The Grove-based outfit are currently fifth in the Constructors' championship, two points ahead of Toro Rosso on 41 points, but a long way behind Force India who lie in fourth on 104 points.
Williams have only achieved one podium this season with 18-year-old rookie Lance Stroll grabbing third place in the Azerbaijan Grand Prix, and Lowe believes their inconsistency has cost them achieving better results.
"Definitely at the half-term report stage we’re not looking as good as we'd like." he said. "We're very disappointed. The car is quicker than that points table would reflect."
"We've seen a lot of variation from circuit to circuit. There are places that we significantly under-perform."