Stonewall told organisations wanting to be included on its equality leader-board to say “parent who has given birth” instead, according to reports.
Documents released to The Telegraph said employers were told they should stop using “gendered language” – such as “mother” and “father”.
It has prompted backlash against the charity, which runs the Workplace Equality Index, with calls for the Government to sever ties with the group.
Marco Longhi, MP for Dudley North, hit out at the move and slammed the “woke brigade’s left-wing agenda” for trying to impose their views.
He said: “Stonewall’s decision to ban the word ‘mother’ is outrageous. This is a continuation of the woke brigade’s left-wing agenda to impose their own views of what society should be – it is a form of Marxism.
“The vast majority of people will reject this nonsense – including many members of the LGBTQ+ community who I have spoken to. I very much look forward to Father’s Day and Mother’s Day in our calendar of festivities.”
The Workplace Equality Index ranks employers based on how inclusive they are judged to be – with a number of Government departments, including the Home Office and the Ministry of Justice, featuring on the list alongside the British Army and MI6.
Stonewall says featuring on the Workplace Equality Index allows employers to understand their employees’ experiences and shows commitment to LGBT equality, with employers achieving a coveted Top 100 spot allowed to use the Top 100 Employers logo to promote their achievement.
Figures from the charity say there are more than 850 organisations, including 250 Government departments and public bodies such as police forces, councils and NHS trusts, signed up as ‘Diversity Champions’.
A spokesman for the charity said in a statement: “All employers need to ensure that their staff, including LGBTQ+ staff, are free from discrimination and prejudice at work, and our Diversity Champions programme is one way for organisations to be supported to meet this requirement.
“Since we set up the Diversity Champions programme in 2001, many large employers have developed major internal programmes to promote diversity and inclusion across their staff and make the workplace better for LGBTQ+ people.
“As with every membership programme, organisations come and go depending on what works best for them at the time, and it’s great that organisations can continue this important work on their own. “
The group added it is “confident in our advice on the Equality Act which is based on the Equality and Human Rights Commission’s Equality Act Code of Practice”.