Ukip opponents are returning flyers using an address they claim is Freepost, while others have chosen to send heavy items, including bricks, in an attempt to rack up a huge postal bill for the party.
Twitter has been flooded with images of people returning flyers, leaflets, unwanted household items and, according to reports, even bricks wrapped in Ukip promotional material after a so-called 'Freepost' address was circulated on the internet.
The address being used is not registered as 'Freepost' on the party's website but was used on a leaflet for a campaign in Norwich in 2010.
The Freepost service allows a person to send mail without affixing a stamp because the recipient chooses to pay the postage fee.
The calls to send Ukip bricks and other items echoed those made in 2011 to send "a brick or a fridge" to the Nottinghamshire Liberal Democrats using their Freepost address, leading the party to announce they had changed their address to one where "unfortunately you will have to use a stamp".
The Nottingham Lib Dems complained after it received up to 300 envelopes, either full of rubbish or empty, but police said sending such items to a Freepost address was not a crime, The Nottingham Post reported.
A spokesperson for the Royal Mail declined to verify if the address being circulated online is still actually a Freepost address for the party. Ukip has not responded to requests for comment.
The UKIP freepost thing works. Just sent them a box of goodies. Should cost them about a fiver. pic.twitter.com/rQkPN9UpWy- Dave Smith (@ffflow) April 25, 2014
The UKIP freepost thing works. Just sent them a box of goodies. Should cost them about a fiver. pic.twitter.com/rQkPN9UpWyDave Smith (@ffflow) April 25, 2014
Sorry UKIP, had to cut mine into 100 pieces to send back to you, hope you enjoy paying freepost for 100 envelopes:) pic.twitter.com/kzIwQ0mSK2Ruaidhrí Quinn (@RuaidhriQ) April 28, 2014
This morning the Ukip leader Nigel Farage announced he will not stand in the Newark by-election sparked by former Tory minister Patrick Mercer's decision to quit over a cash-for-questions scandal.
Yesterday, Mr Farage admitted he was "tempted to stand" and said winning a seat in Westminster would "completely transform the landscape" for his party.
But today he told the BBC: "I don't want to do anything that deflects from the European election campaign, so I am not going to stand in this by-election."