Tearfund is calling upon Deputy Prime Minister Nick Clegg not to backtrack on the UK’s commitment to ending poverty as the UN's summit on the Millennium Development Goals continues in New York.

The development agency said campaigners and development experts were aleady disappointed with an outcomes document on the MDGs, expected to be adopted by world leaders at the summit today.

The document welcomes the progress that has been made on the MDGs - a set of eight development goals with the overall aim of halving global poverty by 2015 – whilst expressing deep concern over the high number of people still living in extreme poverty and hunger, currently more than one billion.

It expresses particular concern at the “alarming” levels of maternal and child mortality and speaks of the determination of leaders to continue working towards the fulfilment of the MDGs despite the financial crisis and “increasing challenges” posed by climate change.

“We are convinced that the Millennium Development Goals can be achieved, including in the poorest countries, with renewed commitment, effective implementation and intensified collective action," it states.

The response among campaigners has been muted. Tearfund said it was full of “positive language” but contained “no tangible promises”.

The organisation's advocacy director, Paul Cook, called on Mr Clegg to use his public statement at the UN to commit the UK to further investment in poverty and climate change.

“We’ve heard our Prime Minister David Cameron say some very encouraging things in the last few days about our moral commitment to addressing global poverty and climate change,” he said.

“Let’s hope that Nick Clegg avoids disappointing billions of people who are living in poverty, and specifies the actions the UK Government will take in order to put this commitment into practice.

"There are so many measures that the MDG document could have listed as concrete plans for the next five years, but instead we are fobbed off with stylish words and no substance.”

The summit has been convened by UN Secretary General Ban Ki-Moon to assess progress on the MDGs just five years before the target date for their fulfilment.

Development agencies, including Tearfund, say that progress on the goals, which include reducing hunger and child mortality rates, has been patchy.

Mr Cook warned that the MDGs would not be met unless governments took “urgent action”, including replenishing the Global Fund established to tackle HIV, TB and malaria, and focusing aid on the provision of clean water and sanitation to prevent more children from dying before their fifth birthday.

He said that tackling climate change would be one of the most significant contributions the UK Government could make, as he called on member states to commit additional funding to help poor communities already being affected by climate change.

He said: "Climate change is often the elephant in the room when discussing global poverty."