The Conservative, Liberal Democrat and Labour manifestos for the 2010 General Election all included the pledge but four years on and nothing has happened.
The idea is only now working its way through parliament after Lib Dem MP Michael Moore brought about the International Development (Official Development Assistance Target) Bill.
At the end of the report stage MPs voted 146 to six to move forward with the plans.
Some say the UK is already meeting the target so it's unnecessary to enshrine the pledge in law.
But Christian Aid's parliamentary and political advisor, Simon Kirkland thinks it vital that Parliament acts. He said: "We don't know what future governments might choose to spend on aid.
"We don't know whether the aid budget may be reduced in future so we think, at this point, it's very important that we legislate to make sure the UK government always has to spend 0.7% in aid as long as it's needed."
The Bill will now move to the House of Lords.