Donald Tusk letter outlines response to Cameron's EU demands
European Council president outlines his response to Mr Cameron's proposals for EU reforms.
European Council President Donald Tusk presented his "new settlement" proposal in talks with Britain on reforms to help keep the country in the 28-nation bloc.
Responding to Prime Minister David Cameron's four objectives put to him in November, Tusk described keeping the unity of the EU as the "biggest challenge".
"The line I did not cross, however, were the principles on which the European project is founded," he added.
Here is the letter in full: