As part of the promotions of their upcoming film Katti Batti, Kangana Ranaut and Imran Khan apparently have to judge a kissing marathon.

Buzz is that the actors will have to find the best kissers from among 50 participating couples who are ready to take on the smoochfest.

As the film is about live-in relationships, this is one of those promotional gimmicks to help people pucker up.

Imran Khan and Kangana Ranaut have kissed for over 24 hours while shooting for the song 'Lip to lip kissiyan'.

The duo kissed in the song for eight hours across three days. The makers are said to have used stop motion technology for the first time in India. The technology which has been used internationally, has been used in the song 'Lip to lip kissiyan', read a statement.

"It's a new technology in India. It was very exciting. The song has shaped up very well. Imran and Kangana both are thorough professionals," the spokesperson of the film said in a statement.