Ukip is investigating comments about the migrant crisis posted on the Twitter feed of one of its election candidates, which suggested that three-year-old Aylan Kurdi died because "his parents were greedy for the good life in Europe".

The remark, on the account of former Ukip election candidate Peter Bucklitsch, from Crowborough, sparked outrage on the social media site and was condemned as "grotesque and awful" by Ukip MP Douglas Carswell.

Meanwhile, Ukip accused a BBC presenter of "prejudice" against the party, after he branded Mr Carswell's own use of language "abhorrent" in a prickly interview about the refugee issue on the News Channel.

The Clacton MP accused interviewer Simon McCoy of a "bizarre rant", while a Ukip spokesman said his comment "reflects on the prejudices of that BBC presenter against Ukip".

The tweet on Mr Bucklitsch's feed came in response to widely-circulated photographs of Syrian refugee Aylan's body lying on a Turkish beach after he drowned with his brother and mother as they attempted to reach Greece by boat.

The post read: "The little Syrian boy was well clothed & well fed. He died because his parents were greedy for the good life in Europe. Queue jumping costs."

It sparked floods of angry responses from Twitter users, who described the comment as "evil", "disgusting" and "horrendous".

But its author did not back down, posting a second message reading: "Predictable unthinking outrage. Turkey is not a place where the family was in danger. Leaving that safe place put the family in peril."

The comment was condemned as "awful" by Liberal Democrat leader Tim Farron, who said: "Appalling lack of compassion. I believe we are a warm hearted & caring nation."

Speaking on the BBC News Channel, Mr Carswell said he had not seen the tweets, but added: "I am aware that some people sometimes say some pretty obnoxious things on social media and if a candidate were to do that they would, I hope, be made an ex-Ukip candidate and slung out of the party.

"It's a pretty grotesque and awful thing to say. I think most reasonable people who saw that image would recognise that we have a duty to act."

A Ukip spokeswoman said that an internal investigation was under way.

There was no immediate response to a request for comment from Mr Bucklitsch, who came fourth in the Wimbledon seat in the May general election, with 2,476 votes.

Mr Carswell told the News Channel Britain had a "moral duty to act" in response to the migration crisis, and called for Parliament to set an annual figure for the number of asylum-seekers it could accept.

Asked what that level might be, the Clacton MP said: "Parliament should decide on that number. There will be some people, like (shadow home secretary) Yvette Cooper - she's opened the bidding at 10,000..."

He was interrupted by Mr McCoy: "'Opened the bidding'? Did you really say that? Did you really use the phrase 'open the bidding'? This is the problem with this. The language surrounding this is so emotive, and careless words upset people."

Mr Carswell replied: "I'm not sure that in a parliamentary democracy... you should take umbrage at me talking about somebody opening the bidding. I'm very comfortable with the use of that language, and I think you taking umbrage perhaps reflects more on you than it does on the crisis."

Mr McCoy responded: "I would rather hope so, because I think the idea of bidding for the number of people fleeing a country for their lives, I find abhorrent. I'm surprised you don't."

Following the interview, Mr Carswell wrote on his Twitter account: "Bizarre rant from BBC interviewer Simon McCoy - guess he was cross I (wouldn't) conform to Guardianista stereotype. Simon prefers to signal his own virtue rather than debate public policy on refugees."

A Ukip spokesman said: "The process of determining how many people can be granted asylum in the UK is conducted on a consultative basis, referring to the expertise of organisations who can best measure both demand and impact, and finally is decided by Parliament.

"To describe Yvette Cooper's suggestion of accepting 10,000 asylum seekers as 'opening the bidding' indicates how that process is carried out. The presenter's indignation at this terminology reflects on the prejudices of that BBC presenter against Ukip rather than any possible perceived offence."