The Covid-19 pandemic is the biggest threat for children as it is rolling back progress on key challenges such as poverty, health and access to education, the Unicef said in a new report on Thursday, representing the biggest global crisis for children since the UN agency was founded 75 years ago.

The widespread impact of the pandemic continues to deepen, the report warned, increasing poverty, entrenching inequality and threatening the rights of children like never before.

"The Covid-19 pandemic has been the biggest threat to progress for children in our 75-year history," said Henrietta Fore, the Unicef Executive Director, in a statement.

"While the number of children who are hungry, out of school, abused, living in poverty or forced into marriage is going up, the number of children with access to healthcare, vaccines, sufficient food and essential services is going down. In a year in which we should be looking forward, we are going backward," he added.

The report showed that Covid-19 has pushed a staggering 100 million more children into poverty -- a 10 per cent increase since 2019. This corresponds to nearly two children every second since mid-March of last year, when the pandemic was declared.

According to Unicef, even in a best-case scenario, recovery to pre-pandemic levels will take up to eight years.

Furthermore, some 60 million children are now living in "monetary poor" households, and more than 23 million have missed out on essential vaccines, the highest number in more than a decade.

Prior to the pandemic, roughly one billion children worldwide suffered at least one severe deprivation, such as lack of access to education, health, housing, nutrition, or sanitation and water. Unequal recovery is pushing the number higher.

The report noted that at the peak of the pandemic, more than 1.6 billion students were shut out of school due to lockdowns.

Worldwide, more than 13 per cent of adolescents aged 10 to 19 are affected by deteriorating mental health. Unicef reported that by October 2020, critical mental health services in 93 per cent of countries were disrupted or halted due to the spread of Coronavirus.

In addition, up to 10 million more child marriages could occur before the end of the decade as a result of the pandemic, while the number of child labourers has risen to 160 million, a nearly 8.5 million increase in the last four years. Rising poverty means an additional nine million boys and girls are also at risk, the report said.

Beyond the pandemic, the report warned of further threats to children that jeopardise their rights.

Unicef said 426 million children globally, or nearly one in five, live in conflict zones which are becoming more intense, with women and girls at the highest risk of conflict-related sexual violence.

Eighty per cent of all humanitarian needs are driven by conflict, the agency added, and nearly half the world's children, some one billion, live in countries that are at an extremely high-risk' from the impacts of climate change.

In the face of the ongoing pandemic, growing conflicts, and the worsening climate emergency, Unicef continues to call for investment in social protection, as well as inclusive and resilient recovery.

Action is needed to end the pandemic and reverse the rollbacks in child education and nutrition, the agency said, including through leveraging its role in vaccine distribution, the report said.