Britain is heading for a confrontation this week at the UN human rights council over its failure to support more than 100 recommendations on subjects ranging from the rights of children to the international law on abortion.

David Isaac, chair of the Equality and Human Rights Commission (EHRC), will attend the UN’s universal periodic review (UPR) of the UK’s human rights record in Geneva, a process which takes place for every country once every five years.

Among the recommendations that the government has declined to back, a number outline the need for the UK to limit how long someone can be held in an immigration detention centre. The UK is the only European country without such a time limit.

Britain has also declined to support recommendations on the detention of children in immigration centres. Of a total of 229 recommendations by UN members, the government will confirm that it is supporting just 96 – 42% of the total. The government has chosen simply to “note” the remainder.

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In 2012, the last time the UK was subject to a review, it supported 54% of the recommendations. The global average for supporting UPR recommendations is 73%. France supported 82% of them at its last review in 2013; Saudi Arabia supported 66%.

Isaac will also warn the UN that the post-Brexit landscape threatens a further deterioration in standards. Although historically Britain has been a champion of human rights, “That reputation is now under threat, due to the negative tone of debate from some politicians and many parts of the media around the Human Rights Act, and the potential risk to people’s equality and human rights protections when the UK leaves the European Union,” he will say.

“The international human rights system provides greater protection for those rights, but the UK government’s continued refusal to fully incorporate the UN treaties it has signed shows scant regard for its international commitments. We are disappointed by the lack of leadership on human rights across the UK government.”

The sharply worded rebuke is likely to focus global attention on the UK’s human rights record at a time when ministers are preoccupied with negotiating a good deal to leave the EU.

The government claims its immigration legislation is in line with obligations under the UN convention on the rights of the child (CRC), but the CRC committee last year disagreed and asked the UK to review its 2016 Immigration Act.

Other measures the government has chosen not to support include a proposal to “ensure that the law governing access to abortion in Northern Ireland fully complies with international human rights law, by decriminalising abortion and ensuring access in cases of severe and fatal foetal anomalies and where the pregnancy is a result of rape or incest”.

A recommendation from Kazakhstan that the UK review the impact of welfare reform on children from disadvantaged families was not supported. The government has explained that “due to methodological and modelling limitations, the UK government does not publish such cumulative analysis for protected characteristics”. However, the EHRC argues that such assessments are both feasible and practicable.

A recommendation suggesting children should be banned from joining the armed forces, in line with its obligations under the optional protocol of the convention on the rights of the child, has also not been adopted. The UK is one of the few countries in the world to allow 16-year-olds to join the armed services.

Civil society organisations, including the British Institute of Human Rights, the Children’s Rights Alliance for England, the Runnymede Trust and Just Fair, have come together to express their disappointment at the government’s position.

In a joint statement to the Observer, the groups state: “Just like us, world leaders are worried about the regressive climate for human rights in our country. Ten countries expressed particular concerns about the perennial threat to repeal the Human Rights Act. Others asked the government to ensure that leaving the EU will not result in lower human rights standards in the UK.”

Sanchita Hosali, acting director of the British Institute of Human Rights, said: “If the UK is to maintain its stance as a global champion of rights, we must welcome and embrace scrutiny of our human rights record here at home. It is disappointing that our government is only willing to support 42% of the UPR recommendations, and certainly does not compare favourably with other countries.”

Louise King, director of the Children’s Rights Alliance for England (CRAE), said: “This is part of a worrying trend of rowing back on crucial human rights protections following threats to repeal the Human Rights Act and a failure to automatically transpose the charter of fundamental rights into UK law through the EU (withdrawal) bill.”

A Ministry of Justice spokesperson said: “The UK has a longstanding tradition of ensuring our rights and liberties are protected domestically and of fulfilling our international human rights obligations. The decision to leave the European Union does not change this.”