Pope Benedict XVI criticised the Equality Bill on Monday for violating “natural law”.

He was thought to be referring to provisions in the bill which would have forced churches to employ gay staff. These were defeated by the House of Lords last week.

The pontiff may also have been referring to laws which banned religious adoption agencies from refusing to serve gay couples. They were forced to abide by the new laws or close.

In a message to 35 Catholic bishops in England and Wales, he said: “Your country is well known for its firm commitment to equality of opportunity for all members of society.

“Yet as you have rightly pointed out, the effect of some of the legislation designed to achieve this goal has been to impose unjust limitations on the freedom of religious communities to act in accordance with their beliefs. In some respects it actually violates the natural law upon which the equality of all human beings is grounded and by which it is guaranteed.”

He urged bishops to defend the church’s “moral teachings”, saying that as the church offered the “truth”, it could not be accused of restricting the freedom of others.

The Pope said: “I urge you as pastors to ensure that the church’s moral teaching be always presented in its entirety and convincingly defended. Fidelity to the gospel in no way restricts the freedom of others – on the contrary, it serves their freedom by offering them the truth.

“Continue to insist upon your right to participate in national debate through respectful dialogue with other elements in society.

“In doing so, you are not only maintaining long-standing British traditions of freedom of expression and honest exchange of opinion, but you are actually giving voice to the convictions of many people who lack the means to express them: when so many of the population claim to be Christian, how could anyone dispute the gospel’s right to be heard?”

The National Secular Society has announced it is planning protests over the Pontiff’s state-funded visit to the UK in September.

NSS president Terry Sanderson estimated that the cost of his visit to taxpayers would be £20 million.

He said: “If the Catholic Church wishes its leader to come here, it should pay for the visit itself. I am sure many others feel the same resentment as we do at the NSS at funding the presence of someone who wishes to impose a reactionary agenda of social change on us.”

Gay groups, women’s groups and pro-choice campaigners are expected to get involved with the protest.

Recently, the Pope criticised Portugal’s new gay marriage law, calling it an “attack” on the natural differences between men and women.

In an end-of year address in 2008, he said that the existence of gay people threatens humanity as much as the destruction of the rainforests does and that “blurring” genders through acceptance of transgender people would kill off the human race. He has also attacked the use of condoms to tackle HIV, saying they may make the problem worse.