Lotus technical director Nick Chester says that development on the Mercedes-powered E23 Hybrid has been hindered by financial constraints at the team in 2015.
Lotus has been beset by money problems this year and was locked out of its hospitality unit in Japan, as it waits for a takeover from Renault.
Chester is sure that Lotus would have competed for higher positions had it been able to sustain development on its 2015 challenger.
"I was pleased with the car in a lot of ways but disappointed in the amount of development," he said.
"We made a good basic car that handled well and with which the drivers could extract the maximum from.
"Unfortunately we have not been able to put developments on it due to finances; we could have gone a lot further with it otherwise and that would have been very interesting to see."
Chester is nonetheless confident that the progress made between the E22 and E23 Hybrid shows Lotus can move forwards in 2016.
"We had learned a lot of lessons in the first year of turbo engines, with the E22, and managed to implement lessons learned to the E23," he explained.
"The 2015 car has always had a good baseline and we have learnt about the direction we want to go. We’ll try and take that forward to next year’s car."