Commonwealth heads of government should press Sri Lanka to improve its religious freedom record, Christian Solidarity Worldwide has said.

The call comes a week before the Commonwealth Heads of Government Meeting (CHOGM) in Colombo, Sri Lanka.

CSW says the situation for religious minorities in Sri Lanka is deteriorating and that the last 18 months have seen a huge rise in violence against Muslims and Christians.

The human rights group says much of the intimidation is linked with the recently formed extremist group Bodu Bala Sena (BBS), or Buddhist Force.

On 11 August, a mosque in the Grandpass area of Colombo was attacked by a Buddhist mob.

There have been 64 recorded acts of violence against Protestant Christians between January and September this year, including arson attacks, church demolitions, mob attacks, and physical assaults.

Administrative regulations have become increasingly strict, with some local officials threatening long-established churches with closure unless they prove their legality.

According to CSW, the government has announced plans to introduce legislation against publications which "defame the original teachings and traditions of the major religions".

A Buddhist Publications Regulatory Board is to be established to regulate any publications suspected of going against Buddhism.

Colombo-based think-tank, the Centre for Policy Alternatives has warned that if the proposals become a reality, they will "stamp a further official seal of approval on Sri Lanka's slide towards majoritarian religious extremism and sectarian violence".

CSW chief executive Mervyn Thomas urged Commonwealth leaders to use their forthcoming meeting as an opportunity to raise human rights concerns with Sri Lanka's government.

"If Sri Lanka is to make meaningful progress on reconciliation and developing a culture of pluralism, it must do much more to address the violence and discrimination suffered by its religious minorities, especially Christians and Muslims," he said.

"With President Rajapaksa due to become the first new Commonwealth Chairperson-in-Office since the adoption of the 2013 Commonwealth Charter, the credibility of this Charter is linked with how far it is respected by Sri Lanka.

"Commonwealth leaders must urge the President to adhere to the principles of the Charter, including human rights (article 2), the need to protect religious freedom (article 4), and the rule of law (article 7).

"They should also strongly encourage the government of Sri Lanka to implement the recommendations made by the UN High Commissioner for Human Rights in her recent report."

Similar concerns have been raised by United Nations High Commissioner for Human Rights Navi Pillay, who recently made a weeklong visit to Sri Lanka.

Following her visit, Pillay told the UN Human Rights Council she was "particularly alarmed at the recent surge in incitement of hatred and violence against religious minorities, including attacks on churches and mosques, and the lack of swift action against the perpetrators".

She noted that the government "seemed to downplay this issue or even put the blame on minority communities themselves" and that she "heard disturbing accounts of state patronage or protection given to extremist groups".

She urged the government "to send the strongest possible signal of zero tolerance for such acts by ensuring that those responsible, who are in many cases easily identifiable, are punished."