International Development Secretary Justine Greening has hinted that the Government may look at reducing aid funding for countries that are not properly collecting taxes.
Ms Greening was being questioned repeatedly about the UK's £500 million aid budget for Pakistan, which has one of the lowest tax collection rates in the world.
She said Britain was helping Pakistan to improve its tax take by sending officials from HM Revenue and Customs to the country but indicated that the Government may have to re-assess aid budgets for countries that are not doing "everything they can".
Ms Greening told BBC One's Sunday Politics show: "I think we will need to look at whether we can keep on funding when a country domestically isn't doing everything it can.
"I want to be clear that the new Pakistan government has been very clear - this is a priority for it and we're going to support them in pursuing that and increasing their own tax take from their own people."
Ms Greening said she was in favour of enshrining the commitment to spend 0.7% of GDP on foreign aid in law.
Pressed on whether the measure which was in the Coalition Agreement would be made law before the next election, Ms Greening said she hopes parliamentary time would allow it.
"At the end of the day we are reaching the 0.7% commitment without needing a law and ultimately we are going to be as accountable as we would be under a law," she said.
"I certainly hope that we can find the parliamentary time to (enshrine it in law) but even if we don't, the key thing is we've acted as if that law is already in place and we're already meeting our 0.7 per cent of GNI (gross national income) on overseas development."