That is the opinion of a leading technical engineer within the championship paddock, who wished not to be named.

On the eve of the first pre-season test at Donington Park, the source told Motorsport.com: “Two squads have as yet had nowhere near enough track running to make their respective packages reliable.”

Season two manufacturers were granted 15 days of private testing to be undertaken before August 1. Six further joint testing days are taking place at Donington this month before the cars leave for the first race in Beijing at the end of August.

The only team known to have utilised all of its testing days is DS Virgin, who completed its program at Guadix last month. The new Anglo-French alliance started track testing in May.

“The manufacturer teams are all confident that they will be starting the season with their new homologated packages, but I know for a fact that quite a few of them are a long way from being competitive, let alone reliable,” said the source.

“Some teams like ABT, DS Virgin and Renault e.DAMS have good resources and good timing plans, but others are struggling massively and I think there is a big element of underestimating what needs to be done.

"I know of two teams that are almost certain to have no other option but to go back to the original package. There will be plenty of all-nighters getting things ready but there is an element of some of them having bitten off way more than they could chew.

"With no testing opportunities after the 25th, some tough calls will need to be made.”

Teams will be allowed to fall back to a default season one powertrain package, but this has to be applied for by the end of the final day of testing on August 25.

An agreement between the teams was formed at a technical meeting at Miami in March to allow competitors this option. One team is believed to have attempted to block this, but were ultimately overruled by series boss Alejandro Agag.

All of the teams must package its cars for ship freighting to Gdansk in Poland on August 31. They will then be transported by train through Russia to China in September, before arriving for the start of the season which is at Beijing on October 17.

This leaves just three weeks for teams to test, develop and potentially modify their new systems.