Yvette Cooper MP has described Boris Johnson's triumph at the Conservative leadership contest as a "deeply depressing" moment.
More than 138,000 Conservative Party members voted in the leadership contest, with a turnout of 87.4 per cent.
Mr Johnson beat his opponent, Jeremy Hunt, by 92,153 votes to 46,656.
He had been the front runner in the contest since Prime Minister Theresa May announced her resignation in May.
The news has been greeted with mixed responses by local politicians.
Yvette Cooper, MP for Normanton, Pontefract and Castleford, tweeted: "Even tho we’ve known this moment was coming, this still feels deeply depressing for the future of our country."
Mary Creagh, MP for Wakefield, described Mr Johnson's victory speech as "Beyond parody."
In a tweet, she said: "The state of this #borisjohnson speech. Bizarre, incoherent and utterly unmatched to the occasion.
"He’s living down to expectations.
"Is it too early to start drinking? Asking for a friend."
But Morley and Outwood MP Andrea Jenkyns, the only Conservative politician to represent part of the Wakefield district, congratulated Mr Johnson on his win, and said it represented "A new dawn for our party, time to deliver Brexit and build a great future for our Country!"
A number of government ministers, including Chancellor Philip Hammond and Justice Secretary David Gauke, had previously said they would resign if Mr Johnson became Prime Minister.