Yet, the UK's foreign aid expenditure of 0.7 percent of Gross National Income (the UN-agreed target for all nations to meet) has been challenged recently by some who question its effectiveness and value to the British public. As a former DFID Minister and as the former Liberal Democrats' Spokesperson on International Development over many years, however, I have seen first-hand what a difference aid makes.

Since 2000 and the adoption of the Millennium Development Goals, the world achieved its commitment to halve extreme poverty. The Sustainable Development Goals adopted globally in 2015 aim to eradicate extreme poverty by 2030, leaving no one behind. That is a supreme challenge. But it is clearly the right thing to do and in our interest. The instability fostered in the world by poverty, migration, climate change, conflict, must be tackled collectively.

This is why my Lib Dem colleagues Michael Moore and Jeremy Purvis took their private member's bill through Parliament in the last days of the Coalition to secure that future commitment of 0.7 percent of GNI on aid. Many members across both Houses helped us, together with NGOs, and tributes are paid to the UK internationally for making this commitment.

So let us look at disease control and elimination - which is just one area that the UK is a world leader in, but which is topical as we pass the fifth anniversary of the London Declaration in 2012, when a major increase of funding for neglected tropical diseases was announced.

UK aid has contributed to the 62 percent decline in malaria deaths between 2000 and 2015, the reduction of Guinea worm infection from 3.5 million people in 1986 to just 22 people in 2015, and played an important role in the near eradication of polio worldwide. For my generation, knowing the fear of polio, and being familiar with those so terribly disabled by the disease here in Britain, that is a stunning achievement. And President Carter, whose work through the Carter Foundation to eradicate the Guinea worm has been so outstanding, stated during a visit to the UK Parliament that he wished to outlive the last Guinea worm. I fervently hope he does.

One example of where this work has been carried forward is the DfID-funded 'Support to National Malaria Programme' or SuNMaP, which worked in partnership with the Nigerian Ministry of Health to reduce the incidence of malaria and strengthen health systems in a country with one of the highest burdens of the disease. The programme, managed by Malaria Consortium (of which I recently became a Trustee), has resulted in the number of pregnant women receiving malaria prevention measures increasing from 45 percent to 80 percent; in addition 40 million long-lasting insecticide-treated mosquito nets have been distributed across the country.

By reducing the incidence of this devastating disease, programmes like this have contributed to the increase in average life expectancy in sub-Saharan Africa from 50.6 years in 2000 to 60 years by 2015. Improvements in health are also estimated to have saved the continent US$18 trillion, according to the World Health Organization's 2016 World Malaria Report, and it is estimated that for every £1 spent on malaria control, £36 is returned in economic benefit. Malaria control is also one of the most cost-effective interventions in global health, costing as little as £3.25 to prevent a case of the disease.

The work of the Global Fund to Fight AIDs, Tuberculosis and Malaria, supported by DfID, is another example of the effective use of aid. In countries where the Global Fund has provided support, HIV mortality rates have declined by 45 percent, and TB mortality rates by 31 percent.

Improving global health abroad benefits UK citizens at home too. By investing in health infrastructure overseas, the UK has increased its own health security in relation to dangerous epidemics, such as Ebola or Zika. These diseases threaten all societies if they are not properly monitored and contained. Improved disease surveillance, better epidemic response and powerful new tools, such as vaccines and better diagnostics, are helping to protect us from the next big global disease threat.

It is clear that there are strong mutual benefits to maintaining the UK aid budget at 0.7 percent. Alleviating poverty, tackling global health challenges and strengthening economies reduce the likelihood of conflict, mass migration and the need to provide aid in the future. For less than one percent of our national income, foreign aid is a low-cost and effective investment that benefits us all.

Lindsay Northover is Liberal Democrat Foreign Affairs Spokesperson in the House of Lords, was a DFID Minister in the Coalition Government, and is a Trustee of Malaria Consortium