Labour has a “severe” problem with anti-Semitism that will get worse if the party’s inquiry into the issue is used as “sticking plaster” to placate voters, the Chief Rabbi has warned.

Ephraim Mirvis criticised the “poisonous invective” and “politics of distortion” of some in the party and said party leader Jeremy Corbyn must take “decisive” action.

Claims by allies of Mr Corbyn that the allegations are a smear were “disheartening”, he said, in an article for The Daily Telegraph.

Mr Corbyn set up an independent investigation into anti-Semitism and other forms of racism within Labour as the row over the handling of controversial comments by prominent figures continued to engulf the party.

The Chief Rabbi wrote: “If this inquiry turns out to be no more than a sticking plaster, designed to placate and diffuse until after the elections this week, the problem will surely get worse and not better.

“Jeremy Corbyn has stated that his party ‘will not tolerate anti-Semitism in any form’, and I very much hope that this inquiry will deliver on that pledge and be followed by decisive action.

“All political parties share in the responsibility to rid our society of anti-Semitism but we cannot achieve that objective with political posturing or empty promises of action never to be fulfilled.”

Mr Corbyn has insisted there is not a ”huge problem” with anti-Semitism in Labour and the issue is limited to a “very small” number of people.

Shadow cabinet minister Diane Abbott said it was ”a smear to say that the Labour Party has a problem with anti-Semitism” and Unite union leader Len McCluskey said Mr Corbyn was the victim of ”a cynical attempt to manipulate anti-Semitism for political aims” that was ”got up by the right-wing press aided and abetted by Labour MPs”.

Mr Mirvis warned it would be a mistake to treat the problem as a “political attack”.

He wrote: “There are many people, from all sectors of our society, who are demanding more responsibility, particularly from our politicians, for stamping out racism and anti-Semitism. The Labour Party has a long and proud history of doing precisely that.

“Yet, comments from senior and long-standing members of the party, both Jewish and not, show just how severe the problem has now become.

“Everyone agrees that there must be no place for anti-Semitism in our politics and I welcome the inquiry recently announced by the party’s leadership. And yet, I would sound an urgent note of caution.

“In recent days, we have heard anti-Semitism in the Labour Party described variously as ‘a smear’ and as ‘mood music’ being manipulated by political opponents of Jeremy Corbyn.

“There has been nothing more disheartening in this story than the suggestion that this is more about politics than about substance. The worst of mistakes, in trying to address this problem would be to treat it as a political attack which requires a political solution.”

He added: “Zionism is a movement celebrated by people right across the political spectrum, all over the world, and requires no endorsement or otherwise of the particular policies of any Israeli government at any time.

“But to those people who have nevertheless sought to redefine Zionism, who vilify and delegitimise it, be under no illusions – you are deeply insulting not only the Jewish community but countless others who instinctively reject the politics of distortion and demonisation.”

Ex-Labour leader Tony Blair said the anti-Semitism controversy had been a “difficult time” for the party.

The former prime minister told Bloomberg TV in Los Angeles: “I know I speak for the overwhelming majority of Labour Party members when I say there’s absolutely no place for anti-Semitism in our party.

“On the contrary, we have always been strong and powerful campaigners against that type of prejudice and that type of poison. It’s been a difficult time, but let’s have this inquiry take its course and I’m sure we’ll come out with some very strong conclusions on this.”