Nigel Farage is facing a formal investigation by the parliamentary standards watchdog over a £5m gift from the crypto billionaire Christopher Harborne.

The Reform UK leader received the money weeks before announcing he would stand as a candidate in the 2024 general election.

Farage has said the gift was intended to cover his personal security costs and therefore did not need to be declared.

However, Labour and other parties argue that MPs are required to declare any potentially relevant gifts or donations received in the 12 months before entering parliament, and that the money from the Thailand-based Harborne falls within these rules.

If the investigation finds Farage committed a particularly serious breach of parliamentary declaration…