If given leave by the court to intervene, the EHRC will argue the way existing human rights and equality law has been interpreted by UK judges is insufficient to protect freedom of religion or belief.
It will say the courts have set the bar too high for someone to prove that they have been discriminated against because of their religion or belief; and that it is possible to accommodate expression of religion alongside the rights of people who are not religious and the needs of businesses.
The Commission is concerned rulings already made by UK and European courts have created a body of "confusing and contradictory" case law. For example, some Christians wanting to display religious symbols in the workplace have lost their legal claim, so are not allowed to wear a cross, while others have been allowed to after reaching a compromise with their employer.
As a result, it is difficult for employers or service providers to know what they should be doing to protect people from religion- or belief-based discrimination. They may be being overly cautious in some cases and so are unnecessarily restricting people's rights. It is also difficult for employees who have no choice but to abide by their employer's decision.
The Commission thinks there is a need for clearer legal principles to help the courts consider what is and what is not justifiable in religion or belief cases, which will help to resolve differences without resorting to legal action. The Commission will propose the idea of 'reasonable accommodations' that will help employers and others manage how they allow people to manifest their religion or belief.
For example, if a Jew asks not to have to work on a Saturday for religious reasons, the employer could accommodate this with minimum disruption simply by changing the rota. This would potentially be reasonable and would provide a good outcome for both employee and employer.
John Wadham, group director, legal, at the Commission, said: "Our intervention in these cases would encourage judges to interpret the law more broadly and more clearly, to the benefit of people who are religious and those who are not.
"The idea of making reasonable adjustments to accommodate a person's needs has served disability discrimination law well for decades. It seems reasonable that a similar concept could be adopted to allow someone to manifest their religious beliefs."
The intervention follows a report for the Commission, which found many people do not understand their rights around religion or belief. The Commission is concerned that this could be preventing people from using these rights.