Daily Mail plans Sunday to fill NOTW gap -source

* Internal dummy run planned for this weekend -source

* Possible names include The Sunday Lite -source

* Ex-Sun editor Kelvin MacKenzie could be a columnist

* Daily Mail already publishes the Mail on Sunday

LONDON, July 14 (Reuters) - Britain's Daily Mail & General Trust (DMGOa.L) is planning a new mass-market Sunday tabloid to fill the gap left by Rupert Murdoch's News of the World, which shut down last weekend amid a phone-hacking scandal, a source close to the situation said on Thursday.

The source said the newspaper group's Associated Newspapers national titles division would do an internal dummy run this weekend and would launch the following weekend if it was a success.

The Daily Mail group did not immediately respond to a request for comment.

The News of the World, owned by News Corporation (NWSA.O), was Britain's most popular Sunday newspaper, with a circulation of about 2.7 million, until it was shut down after 168 years to try to contain an escalating scandal. [ID:nL6E7IE0UD]

Daily Mail already publishes the Mail on Sunday for the mid-market, which it dominates. Its circulation was 1.9 million in May, the latest month for which figures are available.

Names under consideration for the new Sunday title are The Sunday and The Sunday Lite, the source said, adding that ex-Sun editor Kelvin MacKenzie had been mooted as a columnist.

The Internet domain name thesunday.co.uk was registered on July 7 by a party called Colin Wilson Engineering. Sundaylite.co.uk, which was originally registered in 2007, was renewed on July 8 by an individual named Simon Dooner, according to the Whois domain names database.

No further details were provided by the registrants. (Reporting by Georgina Prodhan, editing by Matthew Lewis)