Voters, by a nearly 2 to 1 margin, disapprove of Mayor Bill de Blasio’s handling of the issue of political corruption, according to a poll released Wednesday as prosecutors continue to investigate whether the mayor or his inner circle gave donors preferential treatment on municipal business.

Still, the same poll, by Quinnipiac University, recorded de Blasio’s highest job-approval rating in a year, with more voters than not saying he deserves to be re-elected.

The pollsters found that a similar portion of voters don’t like what de Blasio is doing to tackle the city’s growing homelessness problem, which he first dismissed as tabloid exaggerations but later acknowledged was on the rise.

This week he announced he would open more shelters to tackle the problem.

According to Quinnipiac, 52 percent of voters disapprove of de Blasio on the political corruption issue, compared with 36 percent who approve, and the remainder failing to pick an answer.

It’s the rare issue where de Blasio failed to attract more support than opposition among black voters, his most loyal base, or any surveyed demographic group in the five boroughs.

On city homelessness, which last year reached an all-time recorded high of 60,000 after climbing for years, 55 percent of voters gave de Blasio a bad grade, compared with 26 percent who approved of his efforts. De Blasio announced earlier this week that he’s aiming to reduce homelessness by about 2,500 over five years and build about 90 new shelters.

By a 53-38 percent margin, voters support De Blasio’s so-called mansion tax, which would be 2.5 percent of sale prices of homes or apartments sold for $2 million or more.

At an unrelated news conference in Queens on crime, de Blasio declined to say why the city’s Department of Citywide Administrative Services fired an agency manager, hours after de Blasio was questioned by federal anti-corruption prosecutors on Friday.

The agency has said the firing was unrelated to the mayor’s meeting with prosecutors, and that the administrative agency let him go because of a larger reshuffling.

Nor would he say the extent to which that manager, Ricardo Morales, had dealings with Harendra Singh, the indicted Long Island restaurateur who had also donated to de Blasio’s campaign and is now cooperating with federal prosecutors.

“I’m not going to go into the specifics of that situation, and I don’t know the specifics of that situation,” de Blasio said.

Federal prosecutors are reportedly probing whether Singh wrangled favorable treatment from the administrative services agency on back rent and fines he owed the city.

The New York Times reported that Morales’ work in the agency put him in the middle of two of the roughly dozen matters being scrutinized, including the Singh matter.

De Blasio has maintained that neither he nor his administration committed any wrongdoing and expects to be exonerated.