Labour and the Liberal Democrats’ LGBT groups have criticised UKIP over an election leaflet that mocks bisexuals and attacks same-sex marriage.

Seeking to promote UK Independence Party (UKIP) candidate David Nixon for the Staffordshire ward of Stone Rural in Thursday’s local elections, the leaflet, which was sent to PinkNews by a reader, lists several factually incorrect statements by the Society for the Protection of the Unborn Child (SPUC), an anti-abortion lobby group which is opposed to equal marriage.

The statements include: “Explicit sex education is occurring in our children’s schools. When the ‘Gay Marriage Bill’ becomes law, explicit ‘Homosexual Sex Education’ will have to be taught to keep schools within the law of the 2010 Equality Bill.”

The leaflet illustrated a cartoon of a young boy holding a placard which said: “Rights for Bi-Sexuals We demand the right to marry With (at least) one man and one woman.”

Below it said: “Where will it end? – A child should have the right to a mother and a father.”

Adrian Trett, chair of LGBT+ Lib Dems commented: “The message on UKIP’s leaflet clearly expresses their contempt for universal human rights. The tired clichés regarding bisexuals are beyond insulting and highlight their complete and utter bigotry. Sex education helps young people understand LGBT issues, which is crucial in the battle to eradicate homophobia, biphobia and transphobia in our schools. UKIP’s leaflet undermines the efforts that are being made in this essential area.”

LGBT Labour co-chair, Hannah Blythyn added: “This week we’ve learnt that one of UKIP’s candidates is also a member of the BNP and now we find them distributing homophobic literature. If Nigel Farage wants his party to be credible he must apologise and make sure that his party knows this literature is completely unacceptable. They are totally out of touch with modern Britain.”

Meanwhile, UKIP Gloucestershire County Council candidate John Sullivan has been accused of writing on Facebook that regular physical exercise in schools can “prevent homosexuality” and has congratulated Russia for banning gay pride events by saying: “Well done Russia”.

Mr Sullivan’s comments were made on a Facebook group called “Traditional Britain Group.”

The party is investigating six candidates over links to the BNP and other far-right racist groups.

Ken Clarke, Conservative minister without portfolio, told Sky News on Sunday: “They of course have not been able to vet their candidates. Fringe right parties do tend to collect a number of waifs and strays…

“The trouble with UKIP really is it is just a protest party – it is against the political parties, it is against the political classes, it’s against foreigners, it’s against immigrants. It doesn’t have any very positive policies – they don’t know what they are for.”

Mr Clarke’s comments came after UKIP accused the Conservatives of running a “morally reprehensible” smear campaign against its would-be councillors by trawling through their Twitter and Facebook posts.