The equality watchdog has written to the Green Party asking for more information about a controversial "Zionism is racism" motion passed by members.
The Equality and Human Rights Commission (EHRC) said it recognised that "many Jewish people will be feeling vulnerable" following the motion, passed at the party's conference earlier this month.
The motion described Zionism as an ideology supporting "an ethnonationalist Jewish state in historic Palestine to the exclusion and/or domination of the non-Jewish population".
In a response to the ECHR letter, the party said it "will not discriminate against or exclude people for holding Zionist views" and was committed to tackling antisemitism.
Dozens of Labour and Lib Dem MPs and Jewish campaigners wrote to the regulator raising concerns about antisemitism after the Green motion was passed.
Alongside Jewish groups, the motion was criticised by four of the five Green MPs and two former leaders, one of whom said it was "dangerous" and "divisive".
It piled some pressure on Green leader Zack Polanski in the wake of a by-election defeat. He said the motion was "imperfect" and he wanted to see it amended.
Labour has said it will end power-sharing agreements with the Greens on local councils, unless its councillors disown the motion.
On Thursday, the EHRC confirmed it had written to the Greens following the complaints received.
A spokesperson for the watchdog said: "We have written to the Green Party of England and Wales about its recently adopted 'Zionism is racism' motion to ask for more information and assess its practical implications and potential impact.
"We have received complaints alleging unlawful activity under the Equality Act 2010, including concerns that Jewish people could face discrimination because of their beliefs following the adoption of the motion."
The watchdog said it would "take action where appropriate" after assessing the extra information.
"In the case of the Green Party motion, compliance with the Equality Act is likely to hinge on the practical effects of the motion," the spokesperson added.
In a letter earlier this month, some MPs raised concerns not only about the motion itself but also amendments to protect Jewish Green members at Zionist synagogues being voted down.
"Taken together, these developments raise serious questions about whether Jewish members can participate freely and equally in the party, and whether their religious and communal connections could expose them to complaints or disciplinary action," their letter said.
Separately, the Campaign Against Antisemitism wrote to the EHRC alleging the party had breached the Equality Act through discrimination against Jews.
The campaign group said the motion "effectively states that the state of Israel should not exist" and "defines support for a Jewish homeland in any form as racist".
Having been backed by members, the motion has become party policy but will not necessarily be included in the party's manifesto at the next general election.
In response to the EHRC letter, the Green Party of England and Wales said it "will not discriminate against or exclude people for holding Zionist views" and the motion sets out a political position with "no impact on membership conditions or internal disciplinary processes".
"The party's comprehensive antisemitism guidance, which forms part of our framework of ethics, remains unchanged," a spokesperson added.
"We remain committed to tackling antisemitism and ensuring Jewish members feel welcome and respected."