Young Labour's Equalities Conference was billed as a "one-day event" for disabled, LGBT, women and black, Asian and minority ethnic (BAME) members, according to an invitation sent to members.
However white heterosexual men are not listed as eligible to apply to attend the gathering, set to take place on March 17 in central London.
Labour denied the event is discriminatory because it is being held so that the attending groups can elect equalities representatives for the youth faction's National Committee.
James Cleverly, deputy chairman of the Conservative Party, said: "This is yet another example of discrimination by Labour.
"Their lazy assumption that straight white men can't fight for equality is shocking. It is essential that political parties represent each and every person irrespective of race, sexuality or age.
"The Labour Party should take action now to ensure that this discrimination comes to an end."
Tory MP Ben Bradley also took to Twitter to criticise Labour, however Young Labour Women hit back.
A Labour spokeswoman said: "There is nothing new about spaces for people with protected characteristics meeting to discuss the inequalities and obstacles they face.
"The purpose of this conference is to ensure that members from disadvantaged groups are able to elect representatives to Young Labour's National Committee.
"All other positions on the Committee are elected online, via a 'one member, one vote' system."
The positions of women's, BAME, disabled, and LGBT+ representative will be elected at the Young Labour conference.
Heterosexual white men are not eligible to vote in the elections, as rules state only women can vote for the women's representative and only LGBT members can vote for the LGBT officer.
Additional reporting by Press Association.
