Author Irvine Welsh has insisted he is not "an anti-vaxer" after appearing to question the safety of Covid vaccines. 

The Trainspotting writer was defended himself on social media following criticism after he called vaccines an "iffy product" and urged people not to pretend they come without risk. 

The exchange with his followers on Twitter came after he took umbridge at advice from Boris Johnson during a televised interview to get a booster jab.

Referring to the Prime Minister, Welsh Tweeted: "Make sure you take this sound medical advice on a third dose of an iffy product from a serial liar who couldn’t be arsed to wear a mask in the hospital.

"With the usual boring subtext of “the British people are doing so well but Johnny Foreigner has been letting the side down.”

His followers were quick to question his use of the phrase "iffy product" in relation to vaccines, with one saying: "Iffy product? I never had you down as an anti-vaxer. The boosters are recommended by research and by experienced professionals.

"Thought you were better than that."

Welsh defended his stance, saying: "Okay it’s a great product, it’s saved humanity, Nobel peace prize for our leaders and big pharma execs!

"Obviously nobody would be rushing to take this shit if it wasn’t for a dangerous global virus. Make up your own mind but don’t pretend either alternative carries no risk."

After furter questioning, he later added: "I’m not an anti-vaxer."

Edinburgh native Welsh has written a number of books following the success of his debut novel Transpotting, several of which have been made into films.