More Republicans now have a negative view of the FBI than a positive one, a new poll has revealed in a sign that Donald Trump’s criticism is cutting through.

An online poll found that 47 per cent of Republicans have an “unfavourable” opinion of the FBI while just 38 per cent see it favourably.

It suggests that voters for the Republican Party, traditionally the defender of national security, have followed the US president in souring on the country’s intelligence agencies.

It comes with Mr Trump locked in a war of words with FBI and Justice Department leaders over whether they have shown political bias in the Russia investigation.

The battle has political significance as findings about whether Trump campaign figures acted improperly over Russia in the 2016 election are expected to be published within months.