Sean Dempsey/PA

News International is planning to launch a Sunday version of its popular UK tabloid newspaper the Sun on 29 April, sources have told Journalism.co.uk.

Staff have been secretly working on the new publication since January and it is believed some former News of the World employees (casual and/or full-time) are involved.

News International has declined to comment. After Journalism.co.uk tweeted about the planned launch date last night, the Telegraph’s home news reporter Matthew Holehouse also tweeted that News International would neither “confirm or deny”.

News Int won’t confirm or deny @journalismnews claim that a ‘Sunday Sun’ will launch April 29.

— Matthew Holehouse (@mattholehouse) January 26, 2012

On Monday MP Tom Watson tweeted that a source had told him a “Sunday Sun” was due for launch in April:

A News Corp source tells me Rupert Murdoch has seen the draft designs of the Sunday Sun with a launch in April at a discounted price.

— tom_watson (@tom_watson) January 23, 2012

Update: Journalism.co.uk heard late on Friday (27 January) that the launch date is to be brought forward.