He is in China in his role as Parliamentary Secretary for Foreign Affairs representing New Zealand in Guangzhou at the Second China Pacific Countries Economic Development and Co-operation Forum.
The forum opened on Thursday and is due to finish tomorrow.
Matahiwi Winery owner Alistair Scott, 48, has confirmed his intention to try and wrest the National Party's Wairarapa nomination off Mr Hayes, who will have completed three terms by the time next year's election rolls round.
He said Wairarapa is in need of a strong voice to promote new ideas and needed fresh leadership and new vision.
Should Mr Hayes decide not to put his name up again he will join a long list of National MPs who are standing down.
These include cabinet minister Chris Tremain, Phil Heatley, Kate Wilkinson and four list MPs, being Katrina Shanks, Chris Auchinvole, Cam Calder and Paul Hutchison.
Perhaps the most substantial change will be the departure of finance minister Bill English from the ranks of electorate MPs, as he has decided not to again contest Clutha-Southland, opting instead to become a List MP.
Mr Hayes first won Wairarapa in 2005 with a majority of 2752, increasing that to 6758 in 2008 and again to 7135 in 2011.
Despite his big majority, Wairarapa has been flagged by the Labour Party as one of its top hopes to win from National.