British Foreign Minister has come under criticism as UK lawmakers are expected on June 25 to vote with the government to expand Heathrow airport in London, after decades of debate.
Caroline Lucas, Green party's only MP, called on Boris Johnson to resign.
Conservative MP Greg Hands has tweeted he would be back in London "in time for… vote against #Heathrow expansion."
READ MORE: British Junior Trade Minister Resigns From Government Over Heathrow Expansion
Tory backbencher Sarah Wollaston called on Mr Johnson to take the "principled decision" and resign in order to vote against expanding Heathrow. She also took to Twitter to criticize the Foreign Minister.
Downing Street has so far declined to say where Johnson will be on security grounds.
Prime Minister Theresa May's government agreed to the £14 billion (€15.9 billion, $18.5 billion) plan of adding a third runway at Heathrow, arguing it would provide a major boost to the economy.
Among arguments against the expansion are concerns by many MPs regarding the impact of noise and pollution on a densely populated area.