Ukip leader Nigel Farage has blamed immigration for traffic on M4 that made him miss an event in Port Talbot.
He was expected at a drinks reception as the party prepared to hold its first Welsh conference.
After being for late for more than two hours Mr Farage failed to attend the event.
He later told BBC Sunday Politics Wales: “It took me six hours and 15 minutes in the car to get here. It should have taken three and a half to four.
“That has nothing to do with professionalism. What is does have to do with is a country in which the population is going through the roof, chiefly because of open door immigration and the fact the M4 is not as navigable as it used to be.
“In all these years in Ukip that’s probably about the third event out of a thousand that I haven’t made in time.”
The shadow Welsh secretary, Labour’s Owen Smith, dismissed Mr Farage’s comments as absurd. “Remarks like these are what makes Farage so dangerous. It is clearly absurd to suggest heavy traffic on the M4 is caused by immigration, but through the laughter at his silly comments you can hear Ukip’s dog-whistle politics of division.”
Reacting to Mr Farage’s comments, London Mayor Boris Johnson said: “Of all the excuses I’ve heard for being late, that is one of the poorest.”
He told LBC radio: “Xenophobia is like sewage, it’s a natural concomitant of the human condition. We’ve got to manage it, we’ve got to dispose of it.
“It’s like effluent, it’s something that human beings naturally produce. It doesn’t mean human beings are bad. It’s part of the way human beings are. I think there’s a natural sort of tendency to be alarmed about the Other, the alien.”