Lotus technical director Mike Gascoyne has targeted Williams as the next team to be overhauled after an impressive showing in the Chinese Grand Prix.
Lotus were one of three new teams dramatically off the pace last season.
But after Heikki Kovalainen finished 16th in China, Gascoyne said: "We were genuinely racing and beating established teams on pace.
"Our next target of the mid-division teams is Williams, they're the ones we need to pick off now."
Kovalainen beat Sauber's Sergio Perez and the Williams of Pastor Maldonado at the Chinese Grand Prix, something Gascoyne is confident can become a regular occurance.
Competing as Lotus Racing in 2010, the team finished 10th and were the best of the three newcomers but they failed to score a point.
Kovalainen pleased with Lotus progress
However, in January Gascoyne, a former designer for McLaren, Tyrrell, Jordan, Renault and Toyota, said he believed Lotus could be
competing with Renault
by the end of the season.
So far this season the team owned by Malaysian businessman Tony Fernandes have shown progress with Jarno Trulli taking 13th place in Australia and Kovalainen finishing 15th in Malaysia.
And after an encouraging display in Shanghai, Gascoyne says new upgrades planned for the Spanish Grand Prix in Barcelona on 22 May are likely to see further improvement.
"We're looking at some big updates for Barcelona, we've made a lot of progress recently in the wind tunnel," Gascoyne explained.
"Unfortunately I think the team we are targeting now is Williams.
"I say unfortunately because Williams is a great team and a great name but they're the one we are going to pick off first.
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"We are Team Lotus now and if we are racing Williams well that's good for us."
An interesting statistic for Lotus is that Trulli's best lap in China was quicker than the fastest lap by Ferrari's Fernando Alonso, who finished seventh - Trulli finished 19th.
Team-mate Kovalainen hailed the performance of his Lotus so far this season.
"I'm very pleased. It's good progress and we have just got to keep working hard to improve," said Kovalainen.
"The team has progressed massively from last year. We have left the other new teams behind and are moving on to catch the midfield.
"Only five cars lapped us today and our pace was good all the way through compared to the guys we are targeting in midfield, the Saubers, Williams and even the Force Indias.
"It's excellent progress, very promising and we have just got to keep going in the same direction."