The hope of eradicating polio from the planet by the end of 2012 is in serious doubt, a monitoring committee is warning, because the virus is resurgent in places where it had disappeared and cases continue to rise in Pakistan, one of four countries where it is endemic.

"It is on a knife-edge," said Sir Liam Donaldson, the UK's former chief medical officer who now chairs the independent monitoring board of the Global Polio Eradication Initiative. "Success would be a terrific achievement. To eliminate only the second global epidemic disease [after smallpox] would be a tremendous public health triumph, but failure to do so would have enormous consequences. It is a disease that not only affects individuals and families but erodes economic prosperity in some of the countries affected."

Donaldson considers the continued transmission of polio to be "a global health emergency". Eradicating the disease, he said, "is still feasible but more urgency is needed to complete it. The plan to stop transmission by the end of 2012 is not on track."

The latest report from Donaldson's board, set up last year to monitor and guide the eradication effort, shows that a key target was missed at the end of last year. By the end of 2010, polio should have been stamped out in countries where there had been a resurgence after elimination. It did not happen. The report shows that polio has reappeared in 14 countries.

"The milestone was conclusively missed and the programme must be judged to have performed poorly in this regard," it says.

The biggest concerns are for Chad and Democratic Republic of Congo, with 59 and 80 cases respectively this year. "We are deeply concerned by the situation in DR Congo," says the report. "The worrying picture revealed by vaccination and surveillance data is confirmed by observations of widespread dysfunction on the ground.

"Leadership from the highest level is key for polio eradication and we urge the active involvement of the president in this case. Without his active involvement, we cannot believe that the necessary step-change will occur to interrupt polio transmission in DR Congo."

Polio in Chad, says the report, is widespread and the situation is "of great concern". An emergency action plan has been put into place, but not as quickly as the monitoring board had hoped. The World Health Organisation and Unicef have sent in 100 extra staff to boost vaccination efforts. "The difficult and crucial challenge now is to assemble this new surge of staff into a coordinated functioning team with the utmost speed."Both these countries and 12 others where polio cases have been identified had stopped transmission for at least six months. Four countries have not yet succeeded in doing that – in India, Nigeria, Afghanistan and Pakistan, polio is still endemic.

Excellent progress has been made in India, where mass vaccination days involving more than a million volunteers brought down cases by 94% between 2009 and 2010, from 741 to 42. In the first six months of this year, there has been just one case.

Afghanistan has been doing relatively well in spite of difficulties caused by conflict. Nigeria made excellent progress in 2010, but there has been a loss of momentum following elections, the report says. The leadership is committed, but Kano, in the north, where the Muslim population a few years ago refused immunisation because of false rumours that the vaccine would sterilise their children, "remains a smouldering risk that could yet undermine the whole eradication effort," the board says.

But in Pakistan, cases are going up, not down and conflict and the dismantling of a national ministry of health in favour of local control does not help. "It still looks like it will be the last country to stop transmission, putting its neighbours and the global effort in jeopardy," says the report. "The country needs to muster up relentless energy to really get to grips with the challenges of implementing its emergency action plan."