Voters are frustrated with slow internet speeds and the National Broadband Network has emerged as a surprise winning issue for Labor during the election campaign, analysis shows.

As the final fortnight of campaigning looms, research by media monitor Isentia has revealed that the NBN, the leadership qualities of the major party leaders and asylum seekers are the issues highest on voters' minds.

The analysis reviewed more than 3000 comments on social media and talkback radio since May 8.