The Labour Party has a "serious problem" with anti-Semitism, a senior Labour peer has warned.
Lord Levy told BBC Newsnight he believed anti-Semitism existed across the political divide, but it seemed "more prominent" within Labour.
It follows the party's decision to suspend MP Naz Shah from the party over comments about Israel on social media, pending an investigation.
Ms Shah has made a "profound apology" in the Commons for her remarks.
The MP for Bradford West has been widely criticised for Facebook posts she made before she became an MP, in which she suggested, among other things, that Israel should be moved to the United States.
Lord Levy, who was Tony Blair's envoy and chief fundraiser, told the BBC her comments displayed "ignorance", and he was left "scratching his head with despair as to how people like this can enter our parliament with such a lack of knowledge, discretion and sensitivity".
His comments were echoed by cross-bench peer Baroness Neuberger, who claimed Labour's problem of anti-Semitism was "attached to Jeremy Corbyn becoming leader", and added that it was "an issue with the hard left".
Labour has faced claims of growing anti-Semitism in its ranks. Earlier this year a Labour Luton councillor was suspended from the party after claiming Hitler was the "greatest man in history".
Jeremy Corbyn has insisted anti-Semitism will not be tolerated but some of his MPs say the party leadership is not doing enough to stamp it out.
Shadow education secretary Lucy Powell, Ed Miliband's former chief of staff, told BBC Radio 4's Today programme the party "had to do more" to tackle anti-Semitism and MP Lisa Nandy said it had to be more "pro-active".
But Ken Livingstone - the former London Mayor who is a close ally of Mr Corbyn - said Ms Shah's remarks were not anti-Semitic and the suspension was unnecessary.
He told LBC Radio: "What we have at the moment is a lot of people making a big issue about anti-Semitism in the Labour Party. In 47 years I have never heard anyone say anything anti-Semitic.
"We expelled a couple of people from the Labour Party early on for saying things that could clearly be interpreted as anti-Semitic.
"This is not that; this is an over-the-top comment about the horrendous conflict between the Israelis and the Palestinians."
Lord Levy told BBC London Mr Livingstone was "living on another planet" and "well past his sell-by date" if he believed Ms Shah's comments were not anti-Semitic.
Ms Shah was also defended by George Galloway, the former Respect MP who she defeated at the general election, who said in an article that her comments were "half-witted" but not anti-Semitic, and claims to the contrary were "just another stick to beat Corbyn out of office with".
The former Labour MP said Mr Corbyn and his closest ally shadow chancellor John McDonnell were "lifelong campaigners for Palestinians" but he claimed there was an "establishment" conspiracy to falsely paint them as anti-Semitic.
Initially, Mr Corbyn warned Ms Shah about what he described as her "offensive and unacceptable" posts - but he came under pressure to go further by David Cameron, at Prime Minister's Questions.
Ms Shah, who has quit on Tuesday as an aide to Mr McDonnell, then told the Commons: "Anti-Semitism is racism, full stop. As an MP I will do everything in my power to build relations between Muslims, Jews and people of different faiths and none."
Labour later issued a statement saying Mr Corbyn and Ms Shah had agreed that she was "administratively suspended from the Labour Party by the general secretary", pending an investigation.
"She is unable to take part in any party activity and the whip is removed," the statement added.
In a 2014 Facebook post Ms Shah shared a graphic showing an image of Israel's outline superimposed on a map of the US under the headline "Solution for Israel-Palestine conflict - relocate Israel into United States", with the comment "problem solved".
The post suggested the US has "plenty of land" to accommodate Israel as a 51st state, allowing Palestinians to "get their life and their land back".
It added that Israeli people would be welcome and safe in the US, while the "transportation cost" would be less than three years' worth of Washington's support for Israeli defence spending.
The post was brought to light by the Guido Fawkes political blogging website, which also highlighted a post in which she appeared to liken Israeli policies to those of Adolf Hitler.
Who is Naz Shah?
By Sabbiyah Pervez, BBC Look North
Naz Shah burst onto the political scene during the 2015 general election, where she ousted Respect MP George Galloway.
Her selection as a candidate proved controversial, with divisions emerging in the local party. The candidate who was chosen first stood down four days later, before Ms Shah was imposed by the ruling National Executive Committee.
A bitter campaign followed, with Mr Galloway sparking anger by questioning Ms Shah's account of her forced marriage.
After her victory, she was celebrated locally and nationally for her unique background and life experiences.
Growing up in poverty in Bradford, Ms Shah and her family were abandoned by her father who eloped with a neighbour's teenage daughter. She has spoken openly about her experience of surviving a forced marriage and domestic violence.