The plan to “finish the job” of eliminating the Conservatives from their traditional heartlands at the next election, Ed Davey has promised, saying a further move to the right by a new Tory leader would make this even more likely.

In his first interview since the Lib Dems in the general election, beyond party strategists’ highest predictions, Davey said this expanded Commons contingent – nearly seven times more than their 2019 total – had given them a bigger platform for their message.

Confirming that he intends to lead the party into the next election, Davey said the party would again ruthlessly target so-called blue wall seats, traditionally Conservative areas where the Lib Dems have taken advantage of perceived Tory complacency and disaffection with the party’s ideological direction.

“We need to finish the job at the next election,” he said. “We took down a lot of the blue wall, more than I expected. But there is still some left to take down. We have a real opportunity. I don’t think there has been anybody in this party for over 100 years who could credibly say that.”

With the Lib Dems now fewer than 50 seats behind the , taking another chunk out of Tory strongholds could see Davey’s party targeting second place in the Commons.

“I’m not going to make any predictions,” Davey said. “What I would say is I think the Conservatives are making a compelling case to be consigned to history.”

When the Lib Dems staunchly Tory commuter belt seats in byelections, one of the main drivers was the disquiet felt among more centrist Conservatives about the noisy populism of Boris Johnson and Liz Truss.

This ideological shift seems set to continue, whoever takes over from Rishi Sunak, Davey said: “I think even their most centrist candidate is going to be more to the right than the Conservative party usually is. You get a sense of a party that is still very divided, hasn’t any serious thinking, isn’t prepared to admit mistakes.

“Time will tell, but if they double down, like they look like they’re going to, I think the strategy I’m outlining here is more than credible. Quite where it’ll end, I’m not going to predict. We are not hubristic in any way.”

One positive sign for this tactic of entrenchment and expansion is that the Lib Dems held on to all the byelection seats they took from the Conservatives, despite widespread predictions these would be one-off wins.

Such was the extent of the Lib Dem surge that Helen Morgan tripled her majority , while in two south-west areas that were divided due to boundary changes, the Lib Dems won all four successor seats.

This was, Davey argued, a factor of Lib Dems MPs traditionally being highly energetic and focused in their campaigning, noting that Wes Streeting, the health secretary, this week to “72 new pen pals” on the Lib Dem benches, given the volume of their correspondence about the NHS.

Davey spoke to the Guardian from his office in a suite of rooms inside the main Westminster building, awarded to the party with the third highest number of MPs. The suite had been the Lib Dems’ in the past, but was the base for the SNP’s Westminster group since 2015.

Along with the bigger offices, 72 MPs bring Davey two questions at prime minister’s questions rather than one, and the chance to chair some select committees.

“I’m enjoying the fact that we’ve just got much more influence, more of a voice,” Davey said. “When you’re in politics, you want to get your voice heard.”

Quite what this voice will say is arguably one of the things yet to be fully decided, beyond messages from the election on health and social care and sewage, plus views sometimes to the left of Labour on subjects like the two-child benefit limit and Gaza.

For now, Davey can bask in some of the more unexpected election wins – he said Horsham, which had been continuously Tory since 1876, was “on my very outer limit” of expectations – and oversee the redecoration of the reclaimed office suite, which already has portraits of Liberal and Lib Dem leaders up the staircase.

Another decision remains in the long grass: after a campaign in which Davey , , and his way to media attention, what, if any, stunts might he try next time?

“It’s early days for details of the next election,” Davey said. “People have been kindly offering ideas. Skydiving is one, which we did actually contemplate. Another was going into a tank of sharks, but that is probably not one that came from a friendly source.”