Respondents were "considerably less likely" to back the Liberal Democrats, with only 11 per cent supporting them a few months ago.
Fifteen per cent were undecided, eight per cent backed other parties, five per cent would not reveal their preferences, while just one per cent said they would not vote.
Jonathan Boyd, the JPR executive director, said he was "confident the findings are representative of the Jewish population in Britain as a whole. It demonstrates that the community is multifaceted.
"It also depicts the community as very engaged, and one which takes its democratic responsibilities very seriously. The percentage of people who said they would not vote is very low."
He pointed out that the data "was was not shaped by the leadership TV debates. There is no other data to draw on, so this is the only picture we have."
According to the survey, older Jews were more likely to vote Conservative than those under 40. Jewish men inclined more towards the Conservatives, 36 per cent, compared with 28 per cent for Labour; but the reverse was true of Jewish women, a third of whom declared support for Labour, compared with just 22 per cent for the Conservatives.
Married Jews were "more likely to prefer the Tories,", while single Jews were "more likely to prefer Labour".
The Conservatives were the most popular party for the self-employed, but employees inclined towards Labour.
Jews who described their outlook as "secular" were more pro-Labour than "religious" Jews, who instead preferred the Tories.
There were also significant regional variations, JPR found. "Respondents in Hertfordshire overwhelmingly prefer the Conservatives - 54 per cent - as do respondents in West London - 46 per cent.
"Twenty-two per cent of respondents in south London prefer the Liberal Democrats, twice the national Jewish level. In the north of the UK, including Leeds and Manchester, 35 per cent of respondents prefer Labour, compared with 24 per cent in favour of the Conservatives."
