Nigel Farage has blamed high levels of immigration and the state of the M4 for missing a meet-the-leader event ahead of UKIP's first Welsh conference.
About 100 supporters each paid £25 for Friday's reception to meet the UKIP leader in Port Talbot on Friday evening but he did not arrive in time.
The event at Margam Park was part of his party's conference which was held on Saturday.
Labour criticised Mr Farage calling his excuse "absurd".
Speaking to the BBC's Sunday Politics Wales, Mr Farage said: "It took me six hours and 15 minutes to get here - it should have taken three-and-a-half to four.
"That is nothing to do with professionalism, what it does have to do with is a population that is going through the roof chiefly because of open-door immigration and the fact that the M4 is not as navigable as it used to be."
Shadow Welsh secretary Owen Smith said: "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."