The Equality and Human Rights Commission has launched a formal investigation into the Labour Party over allegations of anti-Semitism.
The watchdog told the party in March it had received a number of complaints and was considering its next steps.
It will now formally look into whether Labour has “unlawfully discriminated against, harassed or victimised people because they are Jewish”.
Labour’s shadow equalities minister says the party will “fully co-operate”.
Dawn Butler said: “The Labour Party at its heart and core is an anti-racist party… so I see this as a way of ensuring, with the scrutiny of the EHRC, that the Labour Party’s rules and policies are robust and fair.”
She added that the investigation would help Labour “build trust with the Jewish community”.
The party has been plagued by accusations of anti-Semitism since mid-2016.
The leadership has been accused of tolerating a culture of anti-Jewish prejudice by a number of its own MPs, some of whom have quit the party in protest.
Leader Jeremy Corbyn has insisted he is getting to grips with the issue and has beefed-up the party’s internal disciplinary procedures.
In a statement, the EHRC said it had “carefully considered the response” it received about anti-Semitism complaints from the Labour Party and would carry out an investigation looking at:
The Muslim Council
The Muslim Council of Britain (MCB) has formally asked the UK’s human rights watchdog to investigate accusations of Islamophobia in the Conservative Party.
In a letter to the MCB said a problem “runs deep into the party”.
The EHRC said in response that it was considering complaints about the party in line with its “usual processes”.
In March, party deputy chairman James Cleverly insisted “immediate action” was taken after any racism claims.
The MCB is an umbrella organisation of various UK Muslim bodies, including mosques, schools, and charitable associations. It has called repeatedly for an independent investigation into discrimination claims.
Now, in its letter filing a formal complaint to the EHRC, it accused the Conservatives of not taking action against Islamophobia shown by Tory MPs, and tolerating discrimination towards party members.
The MCB said there was “sufficient evidence” to suggest the party may have breached anti-discrimination law, and accused it of showing a “callous attitude to complaints”.