The death of hundreds of thousands of British service men and women in the two world wars will have been "in vain" if people do not vote for Ukip, the party has suggested.
An election leaflet sent out in Devon features a photo of British war graves in France with the caption: "They fought and died to keep Britain free from foreign invasion and control by foreign powers.
"Don't let their sacrifice be in vain. Vote Ukip".
The leaflet has been condemned by the party's rivals as "shameful".
"Shameful that British war graves being exploited to drum up votes," Labour MP and former British Army officer Dan Jarvis tweeted. "Offensive and irresponsible."
The leaflet was uncovered by The Sun newspaper which has launched a campaign against the party in the run up to Thursday's poll.
The paper described the leaflet as "sick" in an editorial this morning.
"How dim do you have to be to liken immigration to Britain to an invasion by enemy troops during the world wars?" they wrote.
"And how sick to use the graves of our soldiers for political capital?"
"Ukip's latest Europ election tactic is an outrage. We can't believe Nigel Farage gave it the nod."
The row comes as Farage comes under increasing attack for his comments about Romanians.
On last night's Newsnight he was forced to admit that his repeated claim that 7% of all crime in Europe was committed by Romanian gangs was untrue.
He told the BBC's Nick Robinson on Monday that "across the whole of the European Union, amongst all 28 member states, 7% of all crime is committed by 240 Romanian gangs."
This claim was also repeated in a full page newspaper advert in the Telegraph.
He later admitted to Jeremy Paxman that the claim had been "simplified" but said the public should still be "concerned" about criminals coming from the country.
The Sun's campaign and Farage's recent car crash interview on LBC appears to have given Ukip's opponents the confidence to be bolder in criticising the party.
David Cameron attacked Farage yesterday for his "pretty unpleasant" comments about Romanians, while Ed Miliband accused him of a "racial slur".
Both men stopped short of calling him a racist however. The prime minister said he would "leave it for others to judge" on the matter.
The latest national YouGov poll for the Sun suggests that support for the party may be tailing off. Ukip are on 11% down from 15% last week.
Their latest poll for the European elections also shows the party slipping behind with Labour on 28% and Ukip on 24%.
However, other polls show the party is still on course for victory in the European elections. The final poll for Comres puts the party on 33%, six points ahead of Labour on 27%.