Nigel Farage has said be would not describe migrants as "swarms", just hours after doing so.
Speaking on BBC Radio 4's Today programme, the Ukip leader said he was "not seeking to use language like that" and suggested the Prime Minister was simply trying to appear tough on immigration.
But on Good Morning Britain today he said: "A couple of times I've been sat on the motorway and surrounded by swarms of potential migrants to Britain."
A joint police operation has been launched to target people-smugglers who profit from the desperate migrants trying to reach the UK.
Calais' Mayor has accused Cameron of treating the region with "contempt" - and called on authorities to open the border unless help is given
More fencing and extra sniffer dogs have been sent from the UK to Calais in a bid to curb migrant incursions into Britain.