Gaps in official migration statistics are hampering public debate and policy decisions including on cases relating to human rights laws, according to a leading thinktank.

The University of Oxford’s Migration Observatory has identified 10 areas where information is lacking, including immigration enforcement and returns, and the size of the population living undocumented in the UK.

The research also raised how it is difficult to understand how many immigration cases are affected by the European convention on human rights (ECHR) as the government seeks to change it and Reform and The Tories have pledged to leave it.

An analysis published on Friday found there is little data to identify who and how many people apply for and are granted permission to stay in the UK through the convention, or successfully appeal against their removal.

Madeleine Sumption, the thinktank’s director, said: “The UK’s membership of ECHR is a major issue in public debate, in large part due to its impacts on migration policy.

“But the current data can’t give us a clear picture of where and when it has most impact. This makes it harder for the public or policymakers to make an informed choice about an important decision with long-term repercussions for the UK.”

The research comes after Shabana Mahmood, the home secretary, announced a series of changes to the asylum system and migration rules as she seeks to fulfil Keir Starmer’s pledges to cut the overall number of people coming to the country.

As part of the asylum proposals, ministers will seek to bring in legislation to prevent human rights laws being used to frustrate deportations and make it easier to remove people.

One of the themes the Migration Observatory found in the study were poorly linked records for a person’s migration journey.

Peter Walsh, the thinktank’s senior researcher, said: “These evidence gaps are particularly challenging when trying to track asylum seekers through the immigration system: official data can’t tell us much about what happens to asylum seekers who are refused but not returned, or what type and sequence of appeals some people make when told they must leave the UK.

“These are important questions, especially at a time when the government plans to reorganise the immigration and asylum appeals system.”

Political opponents have criticised the government’s failure to publish missing statistics.

Max Wilkinson, the Lib Dems’ home affairs spokesperson, said: “This confirms what we already knew – the Home Office can’t be trusted to sort things out because it doesn’t even record the data properly.

“When people like Nigel Farage are routinely spreading dodgy claims, it’s even more important that the government knows what’s really going on.”

Chris Philp, the shadow home secretary, said: “Labour are refusing to publish key enforcement data and they avoid saying how many cases are affected by human rights laws. This Labour government is keeping the country in the dark because the truth would expose how weak and incompetent their approach really is.”

A Home Office spokesperson said: “These findings are not acceptable, but they are a product of this government’s inheritance of a migration system that was out of control.

“We are now pursuing major reform to restore order and control at our border, and to ensure our migration system is fair for British citizens. Net migration to the United Kingdom is down by two-thirds under this government, and the removal of illegal migrants is up 23% to nearly 50,000.”