Labour MP John McDonnell has called on the Equality and Human Rights Commission to review its decision to advocate for “compromises” and “reasonable accommodations” for workers who refuse to serve gay people.

He said the move was “outrageous and totally unacceptable”.

Mr McDonnell, who signed an early day motion earlier this week supporting the commission’s move, said some MPs had signed the motion because they believed it was about workers’ rights to wear religious symbols.

He has now tabled an amendment to the motion saying that two of the cases the EHRC hopes to advise on are “not legitimate” and that the body should “ensure that religious belief cannot be used as an excuse for discrimination”.

The EHRC announced last week it would seek to call for “compromises” and “reasonable accommodations” in four cases due to come before the European Court of Human Rights. One involves a Christian registrar who refused to perform civil partnerships and another involves a Christian counsellor who refused to work with gay people.

EHRC legal director John Wadham said compromises and accommodations could be found for religious people in the same way that disabled people are accommodated at work.

Mr McDonnell said: “A real nightmare has arisen over early day motion 2081 which supports the EHRC in its attempt to allow for ‘reasonable adjustments’ on religious grounds. Support has been given by some MPs because they thought that the EDM addressed the wearing of religious symbols by people working in civil society organisations, for example the woman wearing a cross whilst working at BA.

“I have been campaigning for over 20 years to enable Sikhs to wear the Kirpan as part of their religious practice without being discriminated against and so reasonable adjustment in this case seems reasonable.

“However, it is becoming obvious that some are interpreting reasonable adjustment to include the right to discriminate members of the LGBT community. This is absolutely outrageous and totally unacceptable and must be condemned.”

Mr McDonnell, the MP for Hayes and Harlington, is the chair of the parliamentary group of the Public and Communication Services Union, which has written to the EHRC to complain about the proposals for anti-gay staff.

Yesterday, the Trades Union Congress wrote to EHRC chief executive Trevor Phillips to express “deep concern”.

The EHRC’s only LGBT commissioner, former Stonewall chief executive Angela Mason, has not responded to numerous calls and emails seeking comment.