Britain's Secretary of State for Scotland David Mundell arrives at Downing Street in London, Britain, September 13, 2018. REUTERS/Hannah McKay

LONDON (Reuters) - There is a “very strong chance” that Scotland Secretary David Mundell will resign over Prime Minister Theresa May’s Brexit deal, the editor of PoliticsHome.com said on Wednesday without citing sources.

Mundell was among 13 Scottish Conservatives to sign a letter to May saying she needed to deliver “complete control” over domestic fishing waters, adding that Britain must leave the EU’s Common Fisheries Policy after December 2020.