The Bishop of Nottingham, Patrick McKinney, has issued new guidance for schools in the Diocese, around teaching homosexuality and gender issues.
He said it was "not appropriate for our Catholic schools to celebrate Pride as we cannot endorse its entire agenda".
Notts LGBT+ Network said it was "disappointed" with the "regressive" advice.
June is Pride month - a month dedicated to celebrating LGBTQ+ communities all around the world.
The bishop's guidance document states: "It is not appropriate for our Catholic schools to celebrate Pride as we cannot endorse its entire agenda.
"Whilst there is a statutory obligation at secondary level for all schools to include curriculum content on LGBT, there is no legal obligation for them to celebrate Pride."
Martin Stone, a trustee and volunteer for the Notts LGBT+ Network, said: "The Bishop of Nottingham has previously been explicitly clear about the warm welcome that LGBTQ+ Catholics should receive in the diocese.
"To now ban discussions of arguably the most important month in the LGBTQ+ calendar in catholic schools could be seen as a confusing and contradictory decision.
“Pride Month is ultimately a celebration of love, equality and diversity. We have volunteers from multiple faiths and many of them equally associate those attributes with their religious beliefs too, so we’d certainly welcome a discussion with the Bishop of Nottingham about this decision".
'Lord's love'
In a statement, Bishop Patrick McKinney, said: “Every person, without exception, is precious in God’s sight and therefore ours.
"That’s why I have chosen ‘Precious in my sight’ as the title of this document.
“Accompanying students who question their gender is a complex but essential pastoral duty to which the schools of our diocese are very attentive."
"It is my hope that this document will better support those engaged in this important pastoral task [accompanying students who question their gender] and that students will learn that they are deeply loved by the Lord."