Labour's Ceredigion election candidate has apologised "wholeheartedly" for once suggesting "Tippex" be thrown over cars displaying English flags.
Huw Thomas also suggested on a discussion forum in 2006 the flags were for a "simpleton" or a "casual racist".
Earlier this week, he called for Plaid Cymru to replace its candidate for "divisive and hateful language" about some English people living in Wales.
Mike Parker had made his comments in a magazine article in 2001.
UKIP leader Nigel Farage waded into the row, criticising Ed Miliband and saying Friday's development had echoes of a tweet, by a Labour front bench MP during last November's Rochester and Strood by-election, which was branded "snobby".
Emily Thornberry quit her job as shadow attorney general over the message, showing a terraced house with three England flags, and a white van parked outside.
Mr Farage said: "It is clear Ed and his party have learnt nothing from Emily Thornberry and that Labour hate England."
Mr Thomas's views were posted on the Welsh language website 'Maes E'.
Writing during the 2006 football World Cup, Mr Thomas said: "I agree it is totally sickening the number of English flags to be seen around Wales. It really shows the level our society has been infiltrated by immigrants who aren't ready to integrate."
He also stated: "I got the opportunity when I was offered an English flag for half price in WHSmiths Oxford to answer with the sentence 'Since I am neither a simpleton nor a casual racist I must decline your offer.'"
Mr Thomas then had a suggestion for anyone annoyed by flags on cars.
"... TIPPEX - throw a bottle of the stuff over the car, it will look ridiculous (especially if it's a shiny boy racer-ish car), it will take hours to clean it (or money in the car-wash) and, without looking closely, it will look like bird poo!"
In a statement on Friday, Mr Thomas said: "I apologise wholeheartedly for these comments, made while I was a young student. These are not my views now and I deeply regret writing this post online.
"Every candidate at this election will have gone through a political journey. Most will have said or thought things when they were young and at university, college or school that they now regret. This is certainly the case for me."
He added that people in Ceredigion "deserve an MP that will admit when they are wrong".
Responding to the development, Mr Parker said he was "not interested in trying to smear other candidates for what they may, or may not have said".
"This election, for us, is about tackling the Lib Dems, the incumbent MP, on their record as part of the coalition government," he said.
But local UKIP candidate Gethin James said: "I think, in some respects, Huw's comments were worse than the comments that Mike Parker made, because he was inciting people to cause criminal damage to people's cars, and that is certainly not something that someone should be doing."
Liberal Democrat candidate Mark Williams warned the "constant to-ing and fro-ing" was distracting from the real general election issues.
"The people of Ceredigion have to decide which candidate has the strength of character to be their voice in Westminster," he said.
Henrietta Hensher, who is standing for the Conservatives in the constituency, said local people had been let down "by the Welsh nationalists and now by their Labour candidate".
"Only the Welsh Conservatives will be speaking for all people in Ceredigion at this election," she added.
Earlier this week, Mr Parker became embroiled in a row over claims he once compared some English-born residents of rural Wales to Nazis.
Responding to criticism of Mr Parker's comments in a 2001 magazine article that referred to "gun-toting Final Solution crackpots", Plaid's candidate said he would not use such phrases now, as he was "hopefully wiser", but there was nothing to apologise for.
Party leader Leanne Wood condemned what she called a "deliberate attempt to smear" its candidate, but said the words "final solution" were "problematic".
The candidates so far declared to be standing in Ceredigion are: Henrietta Hensher (Conservative), Jack Huggins (Trade Unionist and Socialist Coalition), Gethin James (UKIP), Mike Parker (Plaid Cymru), Huw Thomas (Labour), Daniel Thompson (Green Party), and Mark Williams (Liberal Democrats).