In an appeal to fellow Tory MPs, Stuart Anderson said the only way forward for the party was to stay "united" behind Mr Johnson.
It came after a series of resignations from the PM's administration, sparked by Rishi Sunak quitting as Chancellor and Sajid Javid stepping down as Health Secretary.
Mr Anderson, who won Wolverhampton South West for the Conservatives in 2019, said: "It is not a good sight to see us fighting each other.
"The only way forward is to be united, as when we are divided it doesn't work well for the people who elected us to deliver for them.
"I know not all of my colleagues agree with me but Boris Johnson was elected by the British people and I stand in support of him."
Mr Anderson's comments come after Nicola Richards became the first MP in the Black Country to speak out against Mr Johnson when she resigned as a PPS in the Department for Transport.
And Stafford MP Theo Clarke, another of the 2019 intake, has quit her role as a trade envoy to Kenya, accusing Mr Johnson of showing a "severe lack of judgment and care" in appointing Chris Pincher.
Mr Johnson has vowed to fight on and immediately replaced Mr Sunak with Nadhim Zahawi, while Steve Barclay has succeeded Mr Javid at the Department of Health.
The PM was hit with further resignations this morning. They include Children's Minister Will Quince, and Worcester MP, who has stood down as School Standards Minister.
In a letter to Mr Johnson, Mr Walker said the Government had become "distracted from its core missions by a relentless focus on questions over leadership".
Meanwhile Stone MP Sir Bill Cash told the Express & Star he remains firmly behind Mr Johnson.
Stourbridge MP Suzanne Webb is also continuing to back Mr Johnson. She told the Express & Star: “My position on this remains unchanged.
"I just want to get on with the job and focus on my constituents and my work as a PPS at the Ministry of Defence.
"We have a levelling up bid for Lye about to be submitted. In Parliament we have groundbreaking legislation going through like the Online Safety Bill.
"There is so much good work taking place that is making a difference to people in Stourbridge. We should be concentrating on that."