Image copyright The Scotsman Image caption Pauline Cafferkey was among many British medical staff who risked their lives treating Ebola victims in Sierra Leone

MPs have praised the UK's response to humanitarian crises but said the government cannot always explain how taxpayers' money is being spent.

The Public Accounts Committee said the UK had shown "agility, bravery and innovation" in helping to contain the Ebola outbreak in Sierra Leone and deal with famine in the Horn of Africa.

But performance in war zones like Syria and Yemen needs "fuller understanding".

It also urged the UK to take a lead in trying to simplify UN aid structures.

The UK has one of the largest foreign aid budgets in the world and last year became the first G7 country to meet an international commitment to spend 0.7% - about £12bn - of its national income on overseas development.

The government has sought to refocus spending in recent years amid criticism from MPs on the right of the Conservative Party that the foreign aid budget has been protected from cuts since 2010 during a time of prolonged domestic austerity.

Spending on humanitarian emergencies trebled in the four years to 2014-15, the cross-party committee said in its report. The Department for International Development spent £1.28bn dealing with overseas crises - 14% of its £9.5bn budget.

'Tangible results'

The Department for International Development (DfID), the MPs concluded, was doing a "good job" in responding to more than 20 crises around the world caused by conflict, natural disaster, disease and drought.

It singled out for praise the UK's contribution to fighting the Ebola outbreak, noting that it had quickly mobilised resources to transfer 164 staff from other areas to Sierra Leone - putting some lower priority activities on hold to focus on the crisis.

Image copyright EPA Image caption The UK's assistance to war zones such as Yemen needs better evaluation, the MPs say

Other countries in which "tangible results" had been achieved include the Philippines, where a UK team has been helping build resilience against typhoons following the devastation wrought by typhoon Haiyan in 2013.

The committee acknowledged that DfID was working in many difficult and dangerous environments - but said it did not often know what constituted success in terms of value for money.

The performance of individual interventions is assessed but the committee said protracted engagements in war zones such as Syria and Yemen were not subject to the same "structured approach" as others, limiting the lessons being learnt.

'Held to account'

Among the committee's recommendations are more focus on assessing "longer-running and more complex crises", a review of the use of external contractors, ensuring staff and equipment can always be deployed overseas at short notice, better tracking of how UK funds are spent by other bodies, including UN agencies whose "overlapping remits", the MPs said, can often lead to inefficiency.

"It is important to recognise the Department for International Development has had a positive impact in responding to some desperate situations around the world," said Meg Hillier, the Labour MP who chairs the committee.

"It is also important that, however public money is spent, the government is held to account for that spending.

"In responding to crises, achieving value for money means critical support can be provided more effectively to more of the people who need it. It is vital it looks constantly at the way it spends public money and ensures it is being used to best advantage."

In response, DfID said it welcomed the MPs' recognition "of the success it has had in tackling a range of crises".

"The government's aid strategy places a heavy focus on ensuring value for money, and the UK is playing a lead role in discussions on the future of the international humanitarian system and overseas development, including the role of UN agencies," a spokeswoman added.