Pressure is building on Ukip leader Henry Bolton to resign, with four front bench figures now having resigned following a unanimous vote of no confidence.

Assistant deputy leader Mike Hookem is the latest to leave Bolton's team, joining trade and industry spokesman William Dartmouth, deputy leader Margot Parker, and immigration spokesman John Bickley.

Brexit spokesman and MEP for London, Gerard Batten, has also resigned, calling Bolton's position "untenable" and offering to step in as interim leader, according to the BBC.

Bolton faced calls to step down after the emergence of racist text messages about Meghan Markle sent by his 25-year-old former girlfriend Jo Marney. The couple have since ended their relationship, though Bolton has not ruled out rekindling the romance.

On 21 January, the Ukip national executive committee passed a unanimous vote of no confidence in Bolton, automatically triggering an extraordinary general meeting (EGM) of the party. The meeting, which must be held within 28 days of the vote, will allow members to endorse or reject the no confidence vote, potentially triggering a fresh leadership contest. Members will be told when and where the EGM will take place within the next 10 days.

Bolton has said he plans to continue as leader, arguing that a leadership election would be a costly distraction that could tear the party apart. Speaking on ITV ahead of the vote, he suggested that a vote of no confidence would mean "months of further infighting and further negative media scrutiny". If this were the case, "I think that the reality is that the party is probably over," he said.

If Bolton leaves his position, Ukip would be searching for its fifth leader in 18 months. On his LBC radio show, former leader Nigel Farage questioned whether Ukip could survive another leadership race. Farage is currently in talks with Ukip donor Arron Banks over a new pro-Brexit political movement, though The Guardian reported that the project would not be a traditional political party.

Henry Bolton
Newly elected Ukip leader Henry Bolton speaks at their autumn conference on September 29, 2017 in Torquay, England. Bolton is the UKIP party's fourth leader in just over a year Matt Cardy/Getty Images