A second whistle-blower has come forward with information about US President Donald Trump's dealings with Ukraine. 

The second whistle-blower also worked in intelligence and had firsthand knowledge that supported the original accusations that Mr Trump was using the power of his office to solicit interference from a foreign country in the 2020 US election. 

President Trump and his supporters have rejected the accusations that he did anything improper, remaining defiant amid an official impeachment investigation.