The Liberal Democrat home affairs spokesman, Ed Davey, has accused Theresa May of “bashing the police” as he sought to paint his party as the natural defenders of law and order.

As Lib Dem members gather for their spring conference in Southport, Davey will use a speech on Saturday to step up the party’s attacks on the government over police cuts.

“It should be obvious that a party that is a defender of freedom should be the party of the police, because they protect our freedoms,” he told the Guardian.

He suggested cuts to police numbers under the Tories, together with the government’s Brexit stance, had alienated “soft Conservative” voters, who may now find a home with the Lib Dems.

“I’m extraordinarily worried about what’s happening to our police, both in my constituency and elsewhere. And I’ve long felt that Lib Dem values are more in tune with the police than many people think,” he said. “You have no civil liberties, or they are likely to be significantly reduced, if you don’t have good law and order.

“Mrs May has really bashed the police; she has gone out and picked fights with them, calling them ‘scaremongering’ over police cuts, when actually they were spot on and dead right. That’s not good, when police pay was frozen for such a long time, pensions were cut, officers were lost.

“The approach of the former home secretary, now prime minister, has been pretty anti-police, really. I speak to a lot of police officers who think the Conservatives have lost their way.”

A Downing Street source said: “We have protected police funding and ensured that the police have the powers they need, which several of our political opponents have voted against.”

Davey will also use his speech to suggest there is a social justice argument for increasing funding to the police, pointing out that victims of crime are disproportionately likely to have a disability, be long-term unemployed, from a black or minority ethnic background, or on a low income.

He said the Lib Dems would seek an increase in police funding, with particular emphasis on community policing. “My experience is that the police are there for the most vulnerable. Go through the stats, they’re as clear as can be: the most vulnerable, the less well off in society are more likely to be the victims of crime,.

“So if you want to help them in a very material way, you need good community policing. These people don’t live in gated communities, they don’t have alarms, they don’t have complex insurance on their property. These are people who when they are victims of crime, it has a dramatic effect on their lives. So having police there is actually about creating a fairer country as well as a freer country.”

Support for the Lib Dems is stuck at 7%, according to the latest Guardian/ICM poll, with the Conservatives on 43%, and Labour on 42%.

Davey, who was energy and climate change secretary in the coalition government of 2010-15, said there was frustration that the party had failed to make progress in the polls since last year’s general election under its new leader, Vince Cable, another former coalition minister.

“We think there is a huge gap there; we think we fill it naturally – but it’s not quite happening yet, so there’s a frustration,” said Davey, who pointed out that the Lib Dems had won a number of recent council byelections.

Cable’s predecessor, Tim Farron, had hoped to significantly increase the party’s strength in parliament at the general election, by capitalising on concerns about Brexit.

In the event, the Lib Dems won 12 seats, up from nine, but lost Richmond Park to the Tory Brexiteer Zac Goldsmith, who the party had unseated in a byelection six months earlier.

Davey’s Kingston and Surbiton seat was one of those the Lib Dems regained, after he lost it to the Conservative James Berry in 2015.