LONDON (AP) — British Labour Party leader Jeremy Corbyn is facing growing criticism over his handling of reported anti-Semitism among some of his supporters.

The simmering row escalated Sunday with newspaper reports about numerous anti-Semitic Facebook posts from groups that support Labour. The Sunday Times reports said some senior Labour staff workers were members of Facebook groups that made anti-Semitic and violent comments.

Labour has denied the groups are connected to the party in any way.

Corbyn's leadership has also criticized by longtime Labour activist David Garrard, a major donor. Garrard told The Observer newspaper he has left the party because of its failure to respond to "the most blatant acts of anti-Semitism" by some members.

Corbyn, who represents the left-wing faction of the party, became Labour leader in 2015.