Judges have been criticised by the human rights watchdog for interpreting the law "too narrowly" in high-profile religious discrimination claims brought by Christians.
The Equality and Human Rights Commission (EHRC) said it was seeking to intervene after four Christians took a landmark legal fight over claims of religious discrimination to the European Court of Human Rights.
The commission said it planned to argue that the way existing human rights and equality law has been interpreted by judges has been "insufficient" to protect freedom of religion or belief.
The courts have "set the bar too high" for someone to prove they have been discriminated against because of their religion or belief, the commission said.
It is possible to accommodate expression of religion alongside the rights of people who are not religious and the needs of businesses, the commission said.
The criticism comes after British Airways worker Nadia Eweida, nurse Shirley Chaplin, relationship counsellor Gary McFarlane and registrar Lilian Ladele took their religious discrimination cases to the European Court of Human Rights.
Ms Eweida, a Pentecostal Christian, received widespread publicity when she was sent home in 2006 after refusing to remove a necklace with a cross or hide it from sight.
An employment tribunal ruled Ms Eweida had not suffered religious discrimination, but the airline changed its uniform policy after the case to allow all religious symbols, including crosses.
Mrs Chaplin was moved to a paperwork role by the Royal Devon and Exeter NHS Trust Hospital after refusing to remove a necklace bearing a crucifix.
Mr McFarlane, a Bristol marriage counsellor was sacked for refusing to give sex therapy to homosexuals and Ms Ladele was disciplined after she refused to conduct same-sex civil partnership ceremonies in north London.