A FBI agent who sent text messages to a friend which were critical of Donald Trump has been removed from his senior role in the investigation into Russian interference in the US election.

Peter Strzok, described by The New York Times as being considered one of the most experienced and trusted FBI counterintelligence investigators, was removed from the investigation headed by Robert Mueller this summer.

On Saturday it emerged that the reason for his removal was the discovery of text messages critical of Mr Trump.

The exact content of the messages is not known, but the paper reported that people briefed on the case said Mr Strzok and a colleague reacted to news events, like presidential debates, in ways that could appear critical of Mr Trump.

“Immediately upon learning of the allegations, the special counsel’s office removed Peter Strzok from the investigation,” said Peter Carr, a spokesman for the special counsel’s office.