A former White House official has criticised politicians for advancing discredited conspiracy theories about Ukraine during impeachment hearings.

'I refuse to be part of an effort to legitimise an alternate narrative that the Ukrainian government is a US adversary, and that Ukraine – not Russia – attacked us in 2016,' said Fiona Hill in her opening statement.

Republicans have used the hearings to push the idea that Donald Trump was rightly suspicious of Ukraine because of allegations it attempted to meddle in the 2016 election – a widely debunked claim pushed by some of Trump's closest advisers including his personal lawyer Rudy Giuliani.