The Electoral Commission has opened an investigation into whether the Jeremy Corbyn-backing Momentum movement breached campaign finance rules at the general election.

In a statement, the Commission said it will look at whether or not the campaign group "spent in excess of the spending limits for an unauthorised non-party campaigner".

It will investigate whether far-Left activists submitted a return that "did not include accurate donation information and/or the required declaration stating that the donation return was complete and accurate".

The Telegraph understands that Labour did not authorise Momentum to spend over the targeted spending threshold.

Momentum is a far-Left grassroots organisation set up after the Labour Leader's election victory in 2015. Formed by Jon Lansman, it is strongly supportive of Mr Corbyn and his policies.