International Development Secretary Andrew Mitchell will today reveal that securing progress in the country is his "number one priority" and the cash could speed the withdrawal of troops.
His department is one of only two in Whitehall – along with health – to be protected from swingeing spending cuts being imposed by the Treasury.
But with opinion polls showing most voters want aid slashed before domestic spending, Mr Mitchell is under pressure to justify the protection given to the Department for International Development (DfID). He said: "Nowhere is the case clearer of why well-spent aid overseas is in our national interest than in Afghanistan.
"The UK is there to prevent the Afghan territory from again being used by al-Qaida as a base from which to plan attacks on the UK and our allies.
"While the military bring much-needed security, peace will only be achieved by political progress backed by development."
The extra cash will be focused on stabilising 80 key districts, bolstering the Afghan economy and "getting the government to a place where it can meet the basic needs of its people".
Mr Mitchell also wants to boost education, with an aim of getting six million children into school within two years.
Intensified efforts will be overseen by an aid watchdog, following previous criticisms of the effectiveness of UK-funded projects.
The massive boost in aid comes weeks after the Government was forced to deny splits within the Cabinet over the priorities for the mission in Afghanistan.
Ahead of a visit to the country with Mr Mitchell, Defence Secretary Liam Fox said expectations should be "reset" with security to the fore. "We are not in Afghanistan for the sake of the education policy in a broken 13th-century country," Dr Fox said – but Mr Mitchell insisted development was "absolutely crucial".
According to reports, the DfID is already engaged in a major review of bi-lateral aid, which could see the number of nations receiving help halved to less than 50.
Russia and China were among now-prosperous countries set to lose funds, with some nations in South America and Eastern Europe expected to see help axed entirely.
A survey published last week found more than half of voters thought Britain's international aid budget should be "radically reduced".
Just 29 per cent agreed with David Cameron's decision to protect aid from cuts.
The news comes as further reports revealed British troops are to pull out of Afghanistan by 2014, according to a secret document outlining a blueprint for the withdrawal of coalition forces.
President Hamid Karzai is to announce a timetable for a "conditions-based and phased transition" at an international conference in Kabul this week which will map out the future of the troubled country, according to the leaked communiqu.
The document reportedly states the withdrawal of Nato troops is to begin within months, with the Afghan National Security Forces taking control of military operations by the end of 2014.
The disclosure comes after Foreign Secretary William Hague hinted at British troops leaving Afghanistan by 2014.
The Richmond MP will attend the International Conference on Afghanistan tomorrow, alongside US Secretary of State Hillary Clinton, UN Secretary-General Ban Ki-moon and foreign ministers from more than 70 countries.
The document states: "The international community expressed its support for the President of Afghanistan's objective that the Afghan National Security Forces (ANSF) should lead and conduct military operations in all provinces by the end of 2014."