Euro MP Robert Kilroy-Silk has had a bucket of farm slurry thrown over him by a protester in Manchester.
Mr Kilroy-Silk said he was told the attack was 'in the name of Islam'.
The UK Independence Party member was arriving for a BBC radio show when the attacker emerged from behind a bush.
Fellow guest Ruth Kelly MP was also hit by the slurry. Mr Kilroy-Silk said the man, who later disappeared, claimed he was "doing it in the name of Islam".
In January, Mr Kilroy-Silk quit his BBC One show for remarks he made about Arabs, who he called "suicide bombers".
Mr Kilroy-Silk had already been taken off air by BBC bosses for the comments, in which he also described Arabs as "limb-amputators, women repressors".
The remarks prompted outrage among Muslim groups.
The slurry attack took place on Friday as Mr Kilroy-Silk and Ms Kelly, a Cabinet Office minister and Bolton West MP, arrived at Manchester High School for Girls for the recording of BBC Radio 4's Any Questions.
'Head to toe'
The police were called but the attacker had disappeared by the time officers arrived.
They are treating the incident as assault.
The programme's host, Jonathan Dimbleby, later told the audience the MEP had been covered from "head to toe".
Mr Kilroy-Silk was still able appear to appear on the show after being loaned a change of clothes.
He told reporters he was "very angry" and planned to press charges if his attacker was caught.
Financial Secretary and Bolton West MP Ruth Kelly was also hit
He said the man shouted: "You've offended my religion, I'm doing this in the name of Islam."
"As I started to turn round a guy tipped a bucket of farmyard muck over me and then threw the rest of it over me and the car," Mr Kilroy-Silk said.
"I was totally covered, it was all through my clothes, and it stank to high heaven. It went all inside the car and splattered Ruth Kelly."
A BBC spokesman said: "He took his seat as Jonathan Dimbleby was introducing the show. Fortunately someone at the school had a change of clothes to let him have."
Greater Manchester Police said people near Mr Kilroy-Silk had also been hit by the waste.
Officers took statements at the scene, but no arrests have been made.
Police say the suspect ran off after towards Wilmslow Road after committing the offence but is believed to have been driving a red Vauxhall Corsa earlier.
The suspect is described as white, aged 30 to 40, with a ginger beard. Police want to hear from anyone who has any information.
Mr Kilroy-Silk, an MEP for the East Midlands, resigned the UK Independence Party whip in the European Parliament in October, after criticising UKIP and stating his ambition to be leader.
However, he remains a member of the party.
He said on Friday he hoped to be elected party leader before Christmas.
"I think that is sufficient time for us to put in process what is necessary... in time for us to fight and have a significant impact upon the General Election."
But a UKIP spokesman said that would be impossible under the party's constitution, which requires 70 days before any leadership ballot can take place.