Scots author Irvine Welsh has written an exclusive short story for The Big Issue and other street papers around the world to help tens of thousands of homeless people at Christmas.

Welsh's new tale is called He Ain't Lager and is set during a time after his novels Trainspotting and its sequel, Porno.

The story was specially written for the International Network of Street Papers (INSP), a charity based in Glasgow, Scotland, that supports The Big Issue and 121 other street papers in 40 countries. Welsh is an ambassador for INSP.

The exclusive Christmas story features his infamous character Francis Begbie, portrayed by actor Robert Carlyle in Danny Boyle's eponymous film adaptation of the first book in 1996.

Trainspotting was first published in 1993 and catapulted Welsh to international fame after becoming a cult classic. Porno was released in 2002.

Begbie became infamous for his extreme violence in both novels but readers of He Ain't Lager will be astonished to learn Welsh's psychotic character has been rehabilitated through art and fallen in love.

The plot centres on Begbie visiting his family at Christmas after being released from prison. His brother Joe is homeless.

Welsh - who lives in Chicago, USA - said there were more revelations about Begbie in his new story and urged people to buy The Big Issue.

He said: "I'm not sure where this (story) came from. I never really know. I just think the character has to be full of surprises and I quite like this little twist in his (Begbie) life.

"I became an INSP ambassador not because I'm disadvantaged in the current housing market, but privileged by it; I see so many friends struggling to keep a home together, or trying to rebuild one. They deserve the same rights that I enjoy. Homelessness issues are now sadly ubiquitous across the western world, and very much a product of the weak priorities our political leadership has set.

"The social aspect of housing policy is almost existent, but is in reality how people aspire to live; a home, family, friends, within a community and a concerned citizenry."

Maree Aldam, general manager of INSP, said: "Interviews and writing by famous names give our network of homeless vendors a big sales boost. When Irvine Welsh gave us an exclusive interview earlier this year, it was published in South Africa, Switzerland, Norway, Denmark, Germany and the US - benefiting thousands of vendors.

"So we're delighted that Welsh - now an INSP ambassador - has now chosen to share this instalment of Begbie's life for the benefit of our street papers. We know that the story of this infamous character will appeal to readers worldwide and therefore help our vendors to earn their own living over the winter months."